I recently got to thinking about watching old movies with actors in little bit roles that weren't anything back then but are suddenly noteworthy because the actor went on to become much more famous for something else.
This has happened to me a few times lately where I've gone, "Ooh! Ooh! It's that guy!"
An obvious one is a very young, pre-Buffy/Angel,
pre-Playboy, prepubescent Mercedes McNabb appears a couple of times in the early 1990s movie versions of The Addams Family
& Addams Family Values.
She plays a girlscout selling cookies in the first film and has a sizable supporting role in the 2nd as the stuck up rich girl at camp.
A pre-Sex & the City
Cynthia Nixon also appears in Addams Family Values
as a hippy nanny.
Masi Oka plays a Japanese pedestrian who explains that, due to copyright reasons, the monster chasing them isn't actually Godzilla in Austin Powers in Goldmember.