'The Santa Clause' stars Tim Allen, Eric Lloyd share 9 secrets about filming the Christmas classic Tim Allen and Eric Lloyd describe never-heard-before moments from the movie.

 -- Tim Allen put on a Santa suit and became “the big guy,” nearly 25 years ago for the hit Christmas classic, “The Santa Clause.”

But in all that time since, the lead actors still know a few things about the making of the film that beloved fans may not.

Tim Allen, who played Scott Calvin, and Eric Lloyd, who played his son, Charlie, spoke with “20/20” and share some memories from working on the film.

Here are nine things you may not know about “The Santa Clause.”

1. Tim Allen says kids still tell him what they want from Santa for Christmas

Allen said that when parents recognize him as his Christmas character during the holidays and mention to their children that he’s “Santa,” some kids will pull him aside for a conversation. He said the kids will ask him to tell Santa what they want or that they’ve been good.

“They're smart. They know that I'm associated with him,” Allen said, laughing. “They're almost treating me like they understand there's a transition process.”

2. Tim Allen's daughter thought he was the real Santa Claus

The actor let the youngest of his two daughters watch the film when she was 6 years old, with full disclosure that it was just another role for him and nothing more.

Allen said he told her, “'I don't want you going to school and telling people that your dad's Santa Claus. I play characters just like the TV shows.' ... And she never skipped a beat. She goes, ‘I knew [there] was something special about you.’”

Allen admitted that he told his daughter he filmed with Santa and consulted with him to learn the part.

3. The way that character Scott Calvin became Santa Claus was changed from the original script

In the movie, Scott Calvin, played by Tim Allen, hears some noises on his roof so he goes outside to investigate. When he looks up, he sees Santa Claus looking into his chimney, and he shouts up at him, scaring Santa and causing him to fall. But when Santa hits the ground, he disappears and when Scott Calvin puts on the suit, he becomes the new Santa.

But originally, Allen said his character was supposed give Santa a much more sinister end.

“[Originally], I shot him,” Allen said. “And [DreamWorks CEO Jeffrey] Katzenberg was adamant, ‘We can't start a movie like that.’”

4. The original Santa suit coat was highly crafted, but caused audio issues

“The original coat we did for the first movie was real velvet. It had filigree all over it,” Allen said. “It also had tiny little bells everywhere… [we] didn't really [know] how obnoxious it would be.”

Allen even had to re-record most of the audio in post-production from scenes throughout the film. “I ADRed [Automatic Dialog Replacement] most of that film because people [said], ‘What’s all that ringing?’ And it was me walking.”

5. It took Tim Allen three and a half hours to become Santa

Allen said it took him three and a half hours before shooting started just to get the fat suit and make-up on for scenes when his character Scott Calvin had put on noticeable “Santa” weight.

“I've since then admired Eddie Murphy and Jim Carrey of course -- anybody who's done these fat suits, there's no way to get around how uncomfortable that is,” Allen said. “I don't know how these other guys did it.”

There was even a time limit while shooting, where Allen couldn’t be in the suit for more than six hours due to the lack of ventilation.

Lloyd remembered how long it would take for the makeup team to complete the Santa look and said Allen was a good sport about it.

“I knew about what he was going through with the makeup and everything, because I would have to be in the makeup trailer every day when he would start, or at least I'd be coming in after he had been in there for two hours or something,” Lloyd said. “So, I saw a lot of the transformation.”

6. The first ‘Santa Clause’ was shot in the summer

But over the years with the second and third films, “The Santa Clause 2,” which came out in 2002, and “The Santa Clause 3: The Escape Clause,” which was released in 2006, Allen said, “They got better and better at air conditioning me, just keeping me calm.”

7. Eric Lloyd had to wear fake teeth while filming

Lloyd said he knocked his two front teeth out while attending a Toronto Blue Jays game with his family and they had to change a few already-planned scenes.

“The montage sequence where they're getting [Scott Calvin] ready for his first Christmas, there's a scene where we're dancing down the hallway. That scene had to get pushed up in production because I had knocked my teeth out the night before,” Lloyd said.

Producers changed everything around to start with that montage scene, Lloyd said, and “They cut me out of the end of the scene, and then put all my parts in masters.”

“I was getting to that age where my teeth were falling out, so my bottom two teeth throughout the whole film are all fake teeth, because my bottom two teeth fell out naturally at the beginning of the film,” he said.

He said his orthodontist made “flippers,” which he said were fake teeth that he would “pop in on a wire.”

“There's no real baby pictures of me or adolescent pictures of me without my teeth, because I always had fake teeth for acting,” Lloyd said.

8. Cardboard boxes used as 'safety nets' during stunt scenes

When Scott and Charlie fly in Santa's sleigh in the final scene of “The Santa Clause,” the actors were strapped into harnesses suspended from a giant crane and Lloyd said, “There's not like pads beneath you. There's empty cardboard boxes that are just built up, because when you hit it, the amount of time it takes the air to go out is enough to stop you, more so than a pad or something.”

“But when you look at it, and they pick you up on the wires and you're 15 feet off the ground, they're like, ‘No, no, the cardboard's fine. You'll be fine,’" he said.

9. Tim Allen’s best advice was from Walt Disney

“I remember a long time ago a guy told me that Walt Disney had said, ‘If you can't say it on a one-sheet, it's probably not a very good movie.’ And this is a very simple movie,” Allen said of the hit Christmas film.

He even noted that the simplicity of “The Santa Clause” transcended from the most basic aspects of the movie, like the posters, where Allen is seen standing in front of a white background wearing red pajamas with a Santa hat.

“You get the idea, I'm somehow going to be involved with Santa Claus,” Allen said. "So the comedy's there, but what you're not prepared for, well at least I wasn't, was the emotion of this thing.”