To quote the world’s greatest boss, Michael Scott, it is a “day that will live in infamy.”

In “The Alliance,” the fourth episode of The Office’s first season, the employees of Dunder Mifflin paper company are in a panic over downsizing rumors; Michael, on the other hand, is far more invested in crafting the right joke for Meredith’s birthday card, seeing as he fancies himself a side-splitting comedian and, well, “people are expecting it.”

Suddenly, there’s a knock on his door—it’s Toby from human resources, who wishes to sign the card. When Michael observes Toby pen a joke about Meredith’s red hair, he becomes livid. “I was going to put that in my message, Toby,” he bellows. “So just cross it off. Cross it off now.” Toby abides, crossing the message out, which only makes him angrier. “What are you doing?! Oh come on, you’re ruining it! Toby, come on. Just, look at that. That’s wrecked. Ass.”

“I just go in, write something quickly, and leave—that’s the scene,” recalls Paul Lieberstein, who played Toby. “But it takes me a while to physically write it, and I could just feel him watching me, and feel that burning. Steve [Carell] told me afterwards that it was in that moment that he just decided to hate me so much.”

He laughs. “It’s terrifying acting with Steve. He misses nothing. If you slip in any way, he pounces—just in a fun way, but it’s embarrassing.”

The scene didn’t make the final cut, but Michael Scott’s burning grudge against Toby was born—a vendetta that sparked some of the NBC sitcom’s funniest moments, as well as a popular Twitter account, @TobyHater, that’s amassed over 370,000 followers.

It also convinced Lieberstein, who served in the writers’ rooms of Clarissa Explains It All and King of the Hill before he was hired as a writer and actor on The Office, that he had a warm, likeable screen presence.

That presence was put to the test like never before in Song of Back and Neck, a new film (now available digitally and on-demand) that he wrote, directed, produced and stars in.

“I definitely had trepidation,” says Lieberstein, whose only other sizeable acting gig was on The Office. “You really don’t know if you can carry a movie until you try. There are tremendous actors out there who can’t, and some not-great actors out there who can. So it’s something that I wanted to try.”

Lieberstein plays Fred, a sad loner who, in addition to his miserable job as a paralegal at his father’s law firm, suffers from back pain so debilitating he can barely get out of bed. The tension in his back begins to subside after he visits an acupuncturist and strikes up a romance with Regan (Rosemarie DeWitt), a stunning and kind woman who experiences body aching of her own, and is in the midst of a rough patch with her husband (Brian d’Arcy James).

Like his character in the film, Lieberstein suffered from back pain for decades. It began in his twenties and was so bad that he often couldn’t move his neck, and would have to turn his entire body to look at things. He even found it “dangerous” to drive. He tried several different chiropractors, physical therapists, orthopedic surgeons, massage therapists, and every type of back-roller, but none of it took.

Then his wife gave him a book, and, shortly after joining The Office, he says he came to the realization that his back pain was psychological, caused by stress and suppressed emotion. “In hindsight, it was just so ridiculous how clear it was that it was psychological. I could even connect it to an event, where I couldn’t get up from my chair for two or three hours—like getting script notes on a fax machine,” he recalls.

Fred’s back troubles also turn him into a minor celebrity, as his tension causes the acupuncture needles to emit an ethereal sound when, paired with his acupuncturist’s son on the cello, creates a soothing hymn (no, this did not happen to Lieberstein in real life). Scott Hutchison, the former lead singer of Scottish band Frightened Rabbit, catches Fred and the cellist perform a show at The Mint in L.A., and invites the duo to perform at Coachella.

Less than a month after Song of Back and Neck premiered at the Tribeca Film Festival, Hutchison was reported missing. His body was eventually found on May 10, on a riverbank in Scotland. The news was devastating for Lieberstein, who’d developed a friendship with Hutchison after his Office co-star Rainn Wilson first turned him onto Frightened Rabbit, and then introduced the two.

“Scott and I had lunch, and we just really hit it off,” shares Lieberstein. “He loved the movie, and certainly I loved his music, and saw them in concert a few times.”

“It’s insane. It’s so sad,” he adds, his voice cracking. “It’s hard to watch it now… I wish I had more acting with him, because another part of him seems to come out when he’s doing that. It’s just so… off-beat and beautiful.”

Between Toby and now Fred, many might assume that Lieberstein is despairing and serenity now in real life, but that couldn’t be further from the truth. He’s soft-spoken, yes, but smiles and laughs a ton over the course of our hour-long chat over coffee.

He has reason to be happy. Thanks to Netflix, The Office is more popular now than it’s ever been, and unbeknownst to most casual fans, Lieberstein not only acted as poor ol’ Toby for all 9 seasons of the show, but also served as a writer (penning 16 episodes), director (7 episodes), executive producer (Seasons 4-9), and showrunner (Seasons 5-8).

When I mention how tickled I still am by Michael’s irrational hatred of Toby, he says that he doesn’t quite see it that way.

“I always felt a little different as Toby,” says Lieberstein, chuckling. “To me, it always felt like Toby was the parent of a three-year-old in Michael Scott, who’s constantly having tantrums. He’s just there to be patient, wait it out. Of course it impacts his day, but you can’t get too mad at your three-year-old, so you have to just internalize it.”

Several of the supporting characters on the show, he says, were “created line-by-line”—including Toby, Stanley, Phyllis, Meredith, Creed, and Kelly, played by Mindy Kaling (a fellow writer who scripted the most episodes of The Office, with 21). For instance, Lieberstein and Co. didn’t know that Meredith would be an alcoholic “until we made our first alcohol joke,” or that Michael would hate Toby until that fateful birthday card moment.

Lieberstein left his job as Office showrunner following Season 8 to focus on developing The Farm, an Office spin-off about Dwight Schrute’s beet farm, Schrute Farms. Sadly, NBC passed on the pilot, which instead aired during the ninth season of The Office (“The Farm”).

“It was going to settle into a mockumentary about a small family farm, and trying to make it at a time when they’re being squeezed out—just how rough it is,” Lieberstein tells me. “It would have old characters and new, and they’d have kept the B&B going. It would have been a lot of fun. There was turnover at NBC at the time, and the new regime came in with their own ideas.”

And in case you’re wondering, yes, Lieberstein saw that Office mini-reunion on Saturday Night Live, and though he thinks that a full-on revival of the beloved show might be a bit much, he sounds game for a reunion special.

“I think a one-off special would be the way to go,” he tells me. “Some event that brings everyone back together.”

Until that day comes, he’s hard at work a number of television projects as well as his next film, which he describes as a “murder-mystery.”

“It’s a weird one, so not too far out of my element, I suppose,” he says, flashing a big smile. “Hopefully one of the projects takes off.”