Pendleton originated the role of Motel in the Broadway musical Fiddler on the Roof in 1964, began his film career with Fred the Professor in Otto Preminger's surreal 1968 drug film Skidoo, and co-starred with Madeline Kahn in What's Up, Doc?. Subsequent movie roles included the stuttering public defender in My Cousin Vinny and an ex-chess champion in Searching for Bobby Fischer, and Howard Marner in Short Circuit (with Ally Sheedy and Johnny 5). Pendleton's later film credits include key roles in the Pixar animated feature Finding Nemo, the Academy Award winning A Beautiful Mind, Piccadilly Jim, and Dirty Work.
In 2009, he spoke of his role as Max in an interview with the AV Club:
“I read it and it was sort of a nowhere little part, from the script I read. So I said to my agent, “I’m turning this down.” And she said, “Dear, it’s a movie. You could use this.” It was just that I had played some really good parts in movies, and I didn’t want to play this part. I wanted to wait.
And then the director, his name was Jim Frawley, called me at home and asked what my problem was. I told him “The part doesn’t do anything; he doesn’t go anywhere. He just drives the car and occasionally makes some offhand remark about it.” I told him I’d just had a rough time and I didn’t want to do that. He said, “I know you’ve had a rough time. I’ve been following it.” And his tone was “You really better do this.” And I told him I heard him; I did hear him. But I said I wasn’t up to it right then. So then he called me in about a week and said he’d added a lot to my part; he’d given him a whole arc. I said, “That’s very kind of you.” Then he said, “Now will you do it?” And he described how he’d built the role. So I said okay. It would have been just plain rude if I didn’t.
That was a very unhappy set, because Jim was very unhappy directing that movie. And I noticed that was the only time the Muppet people used an outside person to direct a Muppet movie. They never did that again. After that, it was either Jim Henson or Frank Oz. And I would have liked to have been in one of those, because those sets were very harmonious. But this was not. All my scenes were with Charlie Durning, whom I already knew, because he had a part in Fiddler On The Roof when I was in it, but his part got eliminated out of town. We got to know each other during that. And now of course he’s having quite a film career.”