Actors on stuff from before they were recognizable

I just realized that Nate from Six Feet Under was one of the guys in the limo in the Seinfeld episode where George and Jerry steal a limo pretending to be someone else who turns out to be some big racist author. Also, I saw an episode of Curb Your Enthusiasm with Hurley from Lost playing a drug dealer that sells Larry some pot for his father's glaucoma.

It seem like every actor in a big hit show these days was on Seinfeld at some point, or at least one person from any big show.