A surprising one I noticed recently was a very young Lady Gaga in an episode of The Sopranos (The Telltale Moozadel) as a high school friend of A.J.'s who helps vandalize the school pool. I don’t think she has a line but she’s recognizable.
“Arsenal of Freedom” - Vincent Schiavelli
Also as the wheelchair bound former gangster in “Carlito’s Way”
Also just recently saw Famke Jansen in an old episode of Star Trek the Next Generation… playing a psychic …opposite Professor X–I mean Captain Picard.
On an old 1950’s TV show The Millionaire, DeForest Kelley plays a doctor.
At one point he says “I’m a doctor, not a politician”.
Here’s a direct link to the scene where he says it.
Did we establish from this post that Brad Dourif was not on Taxi?
I just looked that up on IMDB 'cause I’m a huge Dourif fan and I loved Taxi back in the day and I couldn’t figure out when/where/how/why. Dourif is not listed among the cast for any season… And then I cross-checked Dourif’s page and he has no credit for a Taxi role.
ETA: Nevermind. I mis-read TDN’s post and thought it was implying that Dourif had been on Taxi.
There’s a cute little movie in 2005 starring Bow Wow, “Roll, Bounce”, about a big rollerskate-off at a rink, with 70’s music. Paris Hilton can be seen hanging with the rival skate group at the competition. No lines, though. I think she and Bow Wow were friends at some point, only reason I can think she was in it.
Yes, shortly after posting I looked him up. That guy has been in a lot of stuff!
Sorry for the confusion. I was referring to Lloyd and DeVito, and figured that I was the last person on the planet to not know this.
Gandhi.
He was also in Texas Chainsaw Massacre 3, whereas the TCM The Next Generation/Return of the TCM whatever you wanna call it had Renee Zellwinger and Matthew McCongahey (and I’m sure I’ve spelled at least one of those names wrong, but whatever).
Phil from Modern Family played the rich asshole in the Dawn of the Dead reimagining.
Cliff Clavin from Cheers had bit parts in Empire Strikes Back and Superman 2.
Watched Top Gun this past week (why? Because it was on TV!) and in the graduation scene Sundown and Chipper ask each other where Maverick is and for the first time in several watchings of this movie my brain goes “hey, wait, I know that guy!” when I look at Chipper.
It’s Adrian Pasdar.
Blew my mind. Totally justified watching that movie again…as my husband said “see, you can still get something out of Top Gun after all this time!”
A few years back, I was watching reruns of The Magician, Bill Bixby’s early 1970s TV series, and was surprised to see a very young Mark Hamill in one episode.
And I recently watched an episode of the Adam West Batman series, and was startled by Rob Reiner in a bit part.
Character actor Bruno Kirby (who played Carrie Fischer’s b.f. in “When Harry Met Sally”) remarked once on “the David Letterman Show” that Reiner has held very popular industry parties in which all the attendees were requested to bring a video clip of the most embarrassing acting work they’ve ever done. Reiner himself usually submits a clip of himself on “F Troop” playing a hippie folksinger.
Christina Kendricks, most famous for playing Joan Holloway-Harris on “Mad Men”, also appeared on Joss Whedon’s “Firefly” as the recurring character “Saffron” - a con artist who duped Mal Reynolds into believing he’d married her in a blackout.
In the famous finale of “Newhart,” Larry, Darryl & Darryl all get wives. One of the wives is played by Lisa Kudrow (Phoebe on “Friends.”)
Wow, I’m out of touch with television. I still think of her as “Saffron from Firefly who now shows up on that Mad Men show.” But then, I stopped watching TV on TV years ago. Watching it on DVD or the computer is much more flexible.
Also, she was only “Saffron” the first time. The quote marks for the name are very appropriate. 
Nathan Fillion, most famous, of course, for playing Captain Hammer in Dr. Horrible’s Sing Along Blog (oh, and also he is in a cop show and he used to be in a western or a sci-fi show or some such…), was in Saving Private Ryan, where he played Private Ryan.
No, not the Matt Damon one, the first Private Ryan they run into, who has an emotional breakdown thanks to some mistaken identity.
John Ratzenberger, who played Cliff Claven on Cheers, had a very, very small speaking part in The Empire Strikes Back
He was one of the Rebel commanders on Hoth. You might miss him because he is clean-shaven in the movie.
Of course George Reeves was one of the Tarleton twins in the opening scene of “Gone With the wind”. And all New Yorkers like myself who saw this film for the first time in the 1960s instantly yelled “Million Dollar Movie” when the theme song started.
Does Robert Blake as the boy who sells Bogart a winning lottery ticket in “treasure of the Sierra Madre” count? He was one of the little rascals earlier