New York (CNN) Jadon and Anias McDonald, the twins born joined at the head whose separation surgery captivated millions around the world, were gently placed in a red wagon.

They lay side by side, Anias in a blue jumpsuit and Jadon in a gray one. They wore specially fitted white helmets, but there was no evidence of the tubes, IVs or monitors that have been their lifelines since surgery.

Outside the room, more than 30 doctors, nurses and staff at the Children's Hospital at Montefiore Medical Center lined the hallway. A red carpet was rolled out for the boys.

It was time to say goodbye.

Among those on hand Wednesday were lead neurosurgeon Dr. James Goodrich and lead plastic surgeon Dr. Oren Tepper. Both were armed with celebratory baby rattles. Others waved pom-poms and shook tambourines as the boys made their way down the hall of the 10th-floor pediatric intensive care unit (PICU).

The staff had posted a sign on the wall: "Way to go! You did it! We are so proud of you."

Sitting at the front of the wagon was the boys' 3-year-old brother, Aza.

Photos: Conjoined twins separated: New life, apart Anias, left, and Jadon McDonald were born conjoined at the head, something only seen in 1 out of every 2.5 million live births. They were separated in a 27-hour surgery at the Children's Hospital at Montefiore Medical Center in New York in October. Hide Caption 1 of 24 Photos: Conjoined twins separated: New life, apart Nicole and Christian McDonald talk with Dr. Sanjay Gupta in the family waiting area on October 13 as a team worked to separate Jadon and Anias. "When we sent them off this morning, to me, I felt at peace with it and just ready to handle what comes after," Nicole said. Hide Caption 2 of 24 Photos: Conjoined twins separated: New life, apart Dr. James Goodrich Goodrich, left, leads a surgical team as they prepared to separate the twins. "Failure is not an option," Goodrich told the team as they got started. Hide Caption 3 of 24 Photos: Conjoined twins separated: New life, apart Hide Caption 4 of 24 Photos: Conjoined twins separated: New life, apart The twins' surgery was Goodrich's longest craniopagus surgery. It's meticulous, tricky and complex: A single cut too deep can lead to catastrophic bleeding. Hide Caption 5 of 24 Photos: Conjoined twins separated: New life, apart Goodrich's team worked more than 16 hours just to separate the boys, and each continued surgery individually afterward. Hide Caption 6 of 24 Photos: Conjoined twins separated: New life, apart Newly separated twins Anias, left, and Jadon in surgery at the hospital. Goodrich informed the family of the successful separation at about 3 a.m. October 14. "Well, we did it," he told them. When it was official, the room burst into spontaneous applause.

Hide Caption 7 of 24 Photos: Conjoined twins separated: New life, apart Jadon recovers in the pediatric intensive care unit shortly after the surgery. Hide Caption 8 of 24 Photos: Conjoined twins separated: New life, apart Anias returns to his room after his head dressing was changed. Hide Caption 9 of 24 Photos: Conjoined twins separated: New life, apart Jadon stretches his arms in his room within the hospital's pediatric intensive care unit. Anias rests in a nearby bed in the same room. Hide Caption 10 of 24 Photos: Conjoined twins separated: New life, apart Anias, left, stares at Jadon for the first time since the surgery that separated them. Hide Caption 11 of 24 Photos: Conjoined twins separated: New life, apart Nicole McDonald, right, and her mother, Chris Grosso, with Anias in mid-November. Anias had to have his skull cap removed due to infection, but doctors say they are still pleased with his recovery. Hide Caption 12 of 24 Photos: Conjoined twins separated: New life, apart Anias, left, and Jadon lie in a red wagon at the Children's Hospital at Montefiore Medical Center on December 13 as they prepare for the next stage of their journey, two months after their surgery. Hide Caption 13 of 24 Photos: Conjoined twins separated: New life, apart The family was headed to the hospital's banquet hall on December 13, where surgical and pediatric intensive care staff members were gathered for a farewell party. Hide Caption 14 of 24 Photos: Conjoined twins separated: New life, apart Dr. Oren Tepper, the twins' lead plastic surgeon, holds a thank you gift from the McDonald family presented to him at the farewell party. Hide Caption 15 of 24 Photos: Conjoined twins separated: New life, apart Nicole McDonald holds Anias as his twin brother, Jadon, sleeps in the bed to the left. The twins' older brother, Aza, watches television at the hospital from one of the boys' beds shortly before they left for rehab. Hide Caption 16 of 24 Photos: Conjoined twins separated: New life, apart Jadon, left, and Anias McDonald look up at hospital staff as they leave their room at Montefiore Children's Hospital in New York. Their older brother, Aza, proudly sits at the front of the wagon. It was mid-December and they were headed to rehab. Hide Caption 17 of 24 Photos: Conjoined twins separated: New life, apart Nicole McDonald pushes a stroller with Anias as her husband Christian pushes Jadon down a hallway on June 14 at Blythedale Children's Hospital in Valhalla, New York, where the boys have been rehabilitating. Hide Caption 18 of 24 Photos: Conjoined twins separated: New life, apart Anias plays with a toy while laying on a mat in his room at Blythedale Children's Hospital. Hide Caption 19 of 24 Photos: Conjoined twins separated: New life, apart Jadon eats small snacks and drinks from a sippy cup on his own, major progress since he first moved to rehab. Hide Caption 20 of 24 Photos: Conjoined twins separated: New life, apart Nicole McDonald plays with her son Anias as Christian McDonald holds Jadon on a playground outside Blythedale Children's Hospital. Hide Caption 21 of 24 Photos: Conjoined twins separated: New life, apart Nicole McDonald holds Jadon while looking over discharge information on September 1, as they prepare to leave the rehab facility and head home as a family for the first time. Hide Caption 22 of 24 Photos: Conjoined twins separated: New life, apart Nicole McDonald takes Anias into the family's new house for the first time with his older brother, Aza. Hide Caption 23 of 24 Photos: Conjoined twins separated: New life, apart Christian McDonald holds his son Anias as Nicole McDonald checks on Jadon at home with the family dogs, Taz and Tyson. Hide Caption 24 of 24

The boys' father, Christian McDonald, pulled the wagon as their mother, Nicole, walked with them. Both parents paused to hug almost everyone.

The moment stood in stark contrast to the boys' arrival on February 18. On that day, the twins were on a private flight to New York from Illinois. While in the air, Anias stopped breathing and turned blue. Nicole, a pediatric physical therapist, did everything she knew to try to rouse him and worried Jadon would soon be next.

"It was a 10-minute period when all of this was happening where (Anias) was in and out of consciousness," Nicole said.

They were rushed to the emergency room immediately upon landing. It turned out Anias was suffering from a severe strain of the flu.

And now, here the family was, leaving the same hospital amid such jubilation. They were headed to Blythedale Children's Hospital, a specialty facility in suburban New York where they will undergo months of rehabilitation, including physical, occupational and speech therapy.

"It's the most exciting step for me, because I want to see what they can do," Nicole told CNN Chief Medical Correspondent Dr. Sanjay Gupta moments before she left the twins' hospital room for the last time. "We've all come to agreement that it's not goodbye. It's just a see-you-later."

Added Christian, "I'm excited. No ifs, ands or buts about it. I'm just so glad. From this point on, we can actually be all together as a family."

It marked two months to the day since the 27-hour surgery to separate the boys ended on October 14 -- what their dad described as a moment of "hope and a chance for a normal life." It also marked one of the fastest such recoveries on record

Goodrich, who earlier in the day performed craniofacial reconstruction surgery on a 9-month-old boy, acknowledged that he'd miss the twins.

"Am I happy to see them go? No," he said. "But it's time to move on. It's time for the next stage."

'They're so cute'

The day before, Jadon and Anias took a similar wagon ride. It was the first time they'd ever left their room for something non-medical. This time, the staff wanted to throw them a farewell party.

Aza McDonald, 3, crawls into the wagon next to his twin brothers before the party.

The wagon carries meaning for the parents. After they were born, the only way the conjoined twins could be moved was for their parents to pull them in a red wagon. As the months passed, the two could no longer fit in it. They had grown too long.

As they rode Tuesday, they looked up at their mother and held hands. Jadon's head was fully revealed, with none of the bandages that once covered his scalp. Anias, whose skull cap was removed following persistent post-surgical infections, wore a turquoise knit cap.

After a quick elevator ride to the second floor, the boys made their way through a maze of hallways and into the hospital's Grand Hall banquet room.

Awaiting them were more than two dozen staff members, from the nurses and doctors on the surgical team to those in the PICU who've gotten to know the boys best. There were tears and hugs, smiles and moments of glee.

And photos. Lots of photos.

Goodrich, the world's leading expert on craniopagus surgery and the boys' main surgeon, whipped out his iPhone and snapped commemorative shots.

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"It's a pretty emotional day, I've got to say," said Goodrich, who delivered homemade cookies and other treats to the twins' room before the party.

Another guest was Martin O'Malley, a longtime Bronx resident who lives across the street from the McDonalds. He's helped raise donations for the family, delivered them food and felt compelled to join the party.

"It's amazing. It's amazing. It's amazing," said O'Malley, 83, whose twin sister died at birth. "It's hard to imagine just two months ago they were attached. I'm so happy for this family."

Dr. Carrie Stern, a plastic surgeon resident who took part in the surgery, glanced at the boys in the wagon and whispered, "They're so cute. It's just so amazing seeing them from beginning to end."

'So many unknowns'

A week before the party, Nicole and Christian tended to the boys in their room. They couldn't help but wonder about the future for Jadon and Anias.

They know about Carl and Clarence Aguirre, craniopagus twins from the Philippines whom Goodrich separated 12 years ago. With twins joined at the head, one is more dominant, his body working overtime to keep the other twin alive.

Carl was the non-dominant child. He suffered a neurological decline a little over a year after surgery, resulting in permanent disabilities. He speaks only a few words and is confined to a wheelchair.

When the McDonald twins were joined, Jadon was dominant. Since the surgery, Anias has suffered multiple seizures, in addition to having his skull cap removed. He will undergo another surgery when he is 7 to insert bone. For now, his skin is the only thing covering the top of his head, and he will have to wear a protective helmet.

"There are just so many unknowns," Christian said. "We just don't know how it's all going to turn out."

Added Nicole, "Because we know other cases have had that regression, you just hope and pray that that doesn't happen in this circumstance."

The couple gave up their jobs in Illinois and moved to the Bronx to be close to the hospital. When the new year arrives, they'll face a $15,000 insurance deductible, plus whatever unexpected costs might arise. Their apartment lease is up in February, and they don't know whether to renew for another year, because it's unclear how long the boys will be in rehab.

Nicole and Christian McDonald with 3-year-old son Aza and the twins before surgery.

The couple started a GoFundMe page after the twins were born, but after donations swelled to nearly $300,000, the McDonalds told well-wishers to instead help a friend's child in need of a kidney transplant. With the long-term financial reality of their situation sinking in, they are once again receptive to people giving.

"I feel like we've got a long ways to go," Christian said.

He noted that Anias will be cognizant by age 7, aware of the surgery he will have to face to repair his skull cap: "My heart already goes out to him."

Christian and Nicole faced a decision no parent should have to make. Craniopagus twins occur in one out of every 2.5 million births. About 40% are stillborn, and another third die within 24 hours. Of those who survive, 80% die of medical complications by age 2 if not separated.

Mom and Dad said they have no regrets about choosing surgery.

"When you walk into the room and Jadon throws his arms up and wants you to pick him up and you can! He looks at me," Nicole said. "He wiggles from side to side. He giggles. And I can just swoop him up and just hold him and feel his warmth."

Of Anias, she said, "He has really come full circle and begun doing all the things he used to do. And that's been so encouraging, because I always had that worry about Anias."

As she spoke, the boys held hands on a bed where Mom spread them out. At one point, Jadon pulled Anias' hand to his face and then nibbled on his brother's finger. Mom quickly intervened to save Anias from being bitten.

A sense of parental normalcy, when nothing is normal.

After nine months, 'rebirth'

At the goodbye party, doctors, nurses and staff sat around tables, a buffet of chicken, salmon, green beans, mashed potatoes and salad behind them ready for the feast.

Aza bounced around the room, excited for the twins.

All eyes were on Dr. Steven M. Safyer, president and CEO of Montefiore Medicine, as he told Nicole and Christian how the 35,000 Montefiore employees have been rooting for their boys and consider them family.

"I believe that for life, you're members of our world, and this is a wonderful world," Safyer said.

He noted that it's been nine months since he first met the family and that "in a way, this is a nine-month deal. This is the rebirth of these two guys."

Tepper, the lead plastic surgeon, told the crowd he was humbled by the fact that the "McDonalds chose us. They put their trust in us to take care of their boys."

"Hands down, unquestionably, the two leaders of this team are Jadon and Anias," Tepper added. "It's their resilience, it's their determination that steered this voyage. There's a reason the world calls them 'The Little Warriors.' "

Goodrich told the crowd he remembered speaking by phone with Nicole the first time, back when the boys were in utero and she was wondering what could be done to separate them. She told Goodrich she had just one question. Forty-five minutes later, they were still talking: "Totally in tune and all the right questions."

The neurosurgeon thanked everyone in the room, from hospital brass to his team in the operating room to Christian and Nicole. Then he held up a hand-written note he received from Ireland, "to show you how far this story went."

It was addressed simply:

Dr. James Goodrich, surgeon

Children's Hospital Montefiore Medical Center

America

No ZIP code. No city or street address. "Somebody in the postal system got this to me," Goodrich said.

When it came time for the parents to speak, the room grew quiet. Many clutched tissues and dabbed their eyes.

Christian told the group that as grateful as he and Nicole are, they will "never be half as grateful" as their sons.

"Sixteen years down the road," he said, "they're going to be driving their car. They're going to be maybe out on a date. ... Just the fact that they'll be able to go to the bathroom and take a shower by themselves. They're not going to take those things for granted."

It's ordinary for people working their jobs, he said, to not fully grasp the significance of their work.

"Maybe on one of those hard days," he told them, "when it may feel like another day at the office, please know ... you're going to change people's lives, not only individuals' lives for the better, but you're going to impact whole families' lives for the rest of their life. It's a huge thing."

Before the crowd broke into loud applause, Christian ended with a message from his boys: "If I may, I just want to be their voice and say, 'Thank you for giving us, Jadon and Anias, a hope and a chance for a normal life.' "

Then it was Nicole's turn. She wept as she began. She said she had written three pages of material and then tossed it in the trash. "I decided to throw it away and to get up here and to look at you all in the face and tell you just how I feel."

When she was pregnant, she told the crowd, she knew that her boys would be separated and that "this would be the outcome."

"I knew that I would have a miracle. I didn't know how." She repeated, "I didn't know how."

"I prayed every day for God to make the how happen, and you are all the how," she said through tears.

She said that she considered everyone in the room part of her family and that saying goodbye was extraordinarily difficult. "That is a huge testament to you that we don't want to leave here. That's an odd thing that somebody doesn't want to leave the hospital. Everyone is usually itching to get out. We want to stay. I want the boys to talk here first. I want you to see all that, because it was you that contributed to our miracle."

She compared her boys' transition to a caterpillar's metamorphosis into a butterfly.

"Every one of you have been the fiber of that cocoon. You have been what has brought us to this moment: And now they will fly."

There wasn't a dry eye in the room. Nicole handed out gifts, from framed hand-drawn butterfly paintings to photo collages of the boys' progress over the months. Dad tended to Aza while Nicole's mom picked Jadon up and glided around the room with him in her arms.

Many of the workers were on the clock. They scarfed down food quickly because, after all, there are more kids who need their care.

The featured dessert was a cake with white frosting decorated in black with the symbol for infinity, which is also used to represent conjoined twins and, now, the family's infinite love for the hospital team.

"Anias and Jadon," read the black lettering. "God has answered + God has heard."

Plastic surgeon Stern stepped up. Two months ago in the operating room, she was the surgeon who made the final cut that separated the twins.

Now, she made the first cut of the cake that marked the next step of their journey.

Dr. Oren Tepper holds a thank you gift the McDonald family presented to him during the party.

A new space

The boys' wagon ride on Wednesday took them to the lobby of Montefiore, where paramedics and EMTs transferred them to stretchers. Aza jumped onto the stretcher carrying Jadon. More staffers crowded the lobby to send them off.

Two ambulances awaited outside, one for each twin. Aza cried uncontrollably when he had to get off the stretcher as Jadon was being placed in his ambulance.

It was 2:58 p.m. when the twins left. The sun was shining bright over the Bronx on a beautiful 43-degree day.

The ambulances drove together at a steady 20- to 30-mph pace along New York parkways to Valhalla, arriving at Blythedale Children's Hospital at 3:45 p.m.

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"It's almost surreal. I can't believe this is finally happening," Christian said as the boys were wheeled into the new facility. "It's such a big step in the right direction."

Unlike their sendoff at Montefiore, their arrival at Blythedale was tranquil and peaceful.

By 3:49 p.m., the boys were in their new room, spacious and brightly colored, with two beds -- one for each boy -- and two sofas that can fold out into beds for Mom and Dad. It is this facility where the boys will learn how to eat, play and walk.

Nicole held Anias in her arms and marveled at Jadon as he settled into his new bed.

"This is beautiful. I know that the boys will flourish here. It's an exciting step, and we're ready to take off."