Here are a few examples:
* Will Ferrell: While Ferrell was already doing improv comedy during the show's run, he didn't gain widespread fame until later.
* Steve Carell: Carell was a writer on the show, but he didn't have a regular on-screen role.
* Amy Poehler: Poehler got her start in improv, but didn't appear on *The Ben Stiller Show*.
* Tina Fey: Fey started her career in writing, and her most famous work was on *Saturday Night Live* after *The Ben Stiller Show* ended.
This is just a small sample, of course! The world of comedy is vast, and *The Ben Stiller Show* was just one stepping stone for many talented actors.