After 4,200 episodes, there's bound to be a few actors, writers, and staff members who worked on the Street before fame hit. Here are some examples, from Rudy Huxtable to Whoopi Goldberg.

1. Keshia Knight Pulliam (and other kid actors)

Most of the kids who appeared on Sesame Street were "real" children who had proved they could stay oh-so-adorable while working with puppets. But as time went on, more and more child actors were hired, and the more talented kids later found themselves on other popular television shows. Among those kids were Keshia Knight Pulliam (Rudy Huxtable, from The Cosby Show), Tatyana Ali (Ashley Banks, from Fresh Prince of Bel Air), and Tyler James Williams (Chris, from Everybody Hates Chris).

2. Raúl Juliá

Although he was already becoming well known in the world of Broadway, Raúl Juliá appeared as "Rafael", co-founder of the Fix-It Shop (along with Luis) in season 3. Juliá only appeared for one season, while Luis is still a regular on Sesame Street 37 years later.

3. Charlotte Rae

RaÃºl JuliÃ¡ wasn't the only new cast member to Sesame Street in the third season. Charlotte Rae, better known as Mrs. Garrett from The Facts of Life (and before that, Mrs. Garrett from Diff'rent Strokes), portrayed Molly the mail lady. Unfortunately, Molly went the way of Rafael and disappeared by the end of the year.

4. Stockard Channing

Six years before her breakout role as Rizzo in Grease, Stockard Channing appeared on several episodes of Sesame Street as a victim of "The Mad Painter." The Mad Painter was played by Paul Benedict, who had memorable roles in films like Waiting for Guffman and as Harry Bentley on The Jeffersons. Stockard Channing later had another brush with Sesame Street when Elmo, Zoe, Rosita and Big Bird appeared on an episode of The West Wing.

5. Mo Willems

Before he stopped that pigeon from driving that bus, beloved children's author Mo Willems made his name as an animator and writer for Sesame Street. Among his animated sketches were the Suzie Kabloozie cartoons, but his most visible accomplishment was the opening sequence to Elmo's World, which he designed and directed. So, Willems is partly to blame when that theme song gets stuck in your head.

6. Hervé Villechaize

Whenever Oscar the Grouch needed to leave the stoop of 123 Sesame Street, rather than abandon his trash can, he would stick his legs out of the bottom of his can and walk around on his own. Of course Caroll Spinney, his regular puppeteer, couldn't fit inside the can, so a smaller actor was hired to perform Oscar's lower half. Hervé Villechaize portrayed those familiar legs, long before he had to warn Mr. Roarke that "de plane" is coming on Fantasy Island.

7. Pixar

We mentioned Luxo Jr's involvement on Sesame Street in our article about Sesame's fictional celebrity guests, but it bears repeating. Pixar began their reputation as the best CGI animators by creating short films starring their famous lamps Luxo and Luxo Jr. for Sesame Street. The luminous little guys taught lessons about opposites while training their animators to prepare them for Toy Story, which was kind of a big deal.

8 & 9. Richard Belzer and Brian Doyle-Murray

This unlikely duo appeared in an early Sesame Street sketch in which the two men must learn to cooperate in order to keep a cute little dog from ruining their picnic. Do they fail or succeed? Find out for yourself.

10. Whoopi Goldberg

The strangest pre-celebrity connection is that of Whoopi Goldberg, who didn't actually appear on the show until 1990. Years earlier, before she was famous for her stand-up comedy, Goldberg worked backstage as a babysitter, watching over the kids while they waited to be called on set. Post-celebrity, she has worked with Sesame Street in several episodes and made-for-TV specials, and she provides the voiceover for the introductory message at the beginning of every Sesame Workshop home video. Her goodwill has spread to other Muppet productions, including Muppets Tonight, several TV movies, an audio book narration, and a cameo on Muppet Babies. And to think, it all started with a babysitting gig.

A big thanks to Muppet Wiki and ToughPigs for help and images.