In case anyone opened up my blunder and was disapointed, I might as well start this thread.
For me it was Jim Carrey. I remember watching him on In Living Color then BAM!: Ace Ventura, Pet Detective.
I want to go on record (like I haven’t mentioned it before, I know) as saying that my favorite actor in the whole wide world is Sean Astin. He was in The Goonies, the movie that made me fall in love with him (I was eleven). And his most famous movie to date besides that one is Rudy. He’s in the upcoming LOTR movies, so I am sure that the world will come to adore him as I do. So I just wanted to mention that as prrof that I’m not just jumping on the bandwagon and wins fifty million awards because he’s so damn good 
“Hey it’s _______ from…”
Leonardo DiCaprio from Growing Pains
River Phoenix from Seven Brides for Seven Brothers
Jim Carrey from The Duck Factory
Carrie-Ann Moss from Models Inc
David Duchovny from Twin Peaks
Robert Downey Jr from Weird Science
Hey, its Geena Davis from that episode of Knight Rider and then Family Ties.
Shelley Long made carpet ads before Cheers. She was in her prime–RRRRRRRROWWWWWWWW!
Richard Dreyfuss in American Grafitti, The Apprenticeship of Duddy Kravitz, and then in Inserts.
Geena Davis from “Buffalo Bill”
No, no, no. Jim Carrey was in Once Bitten. Oh sure, it came out a year after The Duck Factory, but no one can forget this classic piece of cinema.
Also, I remember Jason Alexander from a McDonald’s commercial. How pathetic is that?
Being a SNL watcher, I knew who Julia Louis-Dreyfus was before Seinfeld, and who Damon Wayons was before In Living Color (he was also in the movie Roxanne).
I’ve known Tom Hanks since his days on Bosom Buddies. There are also a number of comedians I’ve known since they were doing standup. Drew Carey, Bob Saget, and more recently Ray Romano are a few that immediately come to mind, there are others. In fact, I remember Drew Carey’s appearance on Star Search (don’t remember if he won anything, though).
River Phoenix from Seven Brides for Seven Brothers?!! I thought that movie was made before he was born.
Well, he’s only a minor celebrity, but the first that comes to mind is William Ragsdale, star of the movie Fright Night and the TV series Herman’s Head and Brother’s Keeper. Bill was a senior at Hendrix College when I was a freshman, and there were stories in the college paper over the next few years as he got acting roles (national touring company of Biloxi Blues, etc.). Then Fright Night, then . . . . Nothing for a few years. He was working, just not in film or anything that would attract national attention (supposedly, he was close to being cast in the lead in the film of Biloxi Blues, only to have Matthew Broderick pull it out from under him). The next I heard of him was sometime after Herman’s Head hit the airwaves.
Along the same lines, another Hendrix alum from my days there, Natalie Canerday, has had several feature film roles, most notably the mother of the little boy in Sling Blade (she was also in an earlier Billy Bob Thornton-written flick, the extremely underrated One False Move, as the wife of one of the main characters). She’s also been in Biloxi Blues (the girl Eugene dances with at the very end of the movie), October Sky, Dwight Yoakam’s South of Heaven, West of Hell, and a few others.
Janeane Garofaolo (sp?) Saw her on some MTV stand-up comedy special and have been in love ever since.
The only one I can think of off hand is seth green. He was Dr Evil’s son in Austin Powers and has played in numerous other movies, most recently rat race. I was actually good friends with him when I was about 10 or so. We went to camp together and at the time he was doing tv shows like amazing stories and some cartoon voices. His big role at the time was radio days. The last time that I saw Seth was at his bar-mitzvah (13 years old). His career seemed to fade for awhile then I heard he moved from philadelphia to LA and next thing I knew he was in a ton of movies and TV shows. It gives me a chuckle whenever I get to see him in a movie. One of my friends actually still keeps in touch with him.
Got ya beat. Been following him since high school.
Claudia Christian from way back when she was in Berenger’s.
Tom Hanks from Bosom Buddies.
Soap fan here. We get to see them all before they hit the big time.
Most notably, I was a huge fan of Demi Moore on General Hospital in 1982; Janine Turner, also on GH in 1982; Anne Heche on Another World 1987-1990 (I even have tapes). Watched Luke Perry on AW in the late '80’s, although I don’t really remember him because his role was pretty insignificant, also saw Spencer Treat Clark of Gladiator on AW during the '90’s. Oh, Thomas Gibson of Dharma and Greg was on AW in the '90’s too.
There are tons more that I can’t think of at the moment. My prediction for next big breakout star is Tammy Blanchard, formerly of Guiding Light, who is Emmy-nominated for her TV-movie role as the young Judy Garland this year.
I remember watching Ethan Hawke and River Phoenix in Explorers back in '85 and being impressed. Great performances for little kids.
And then there was that episode of Kung Fu, and this one gunfighter, who just looked amazingly studley. I had bad deja vu when I saw Star Wars, and finally looked it up to make sure years later… yup. Harrison Ford. In Kung Fu.
I had a huge crush on Leonardo DiCaprio beginning with Growing Pains. I followed him through What’s Eating Gilbert Grape?, This Boy’s Life, Total Eclipse, The Quick and the Dead, The Basketball Diaries, Marvin’s Room, and Romeo & Juliet, his big role that got the teenage girls panting. By the time Titanic rolled around, he caused only slight heart palpitations.
This was pre-AOL, pre-job, pre-17. I paid people to sneak me into his R-rated movies. I must have spent several hundred hard-earned allowance dollars on magazines with articles or pictures of him. All were plastered on my wall, culminating in a huge bulletin board collage with about two hundred pictures. I kissed every one good night, every night.
Ah, Leo. I still get a tad bit jealous when I hear about him with Gisele.
I’ve also loved Elijah Wood since Radio Flyer and Avalon, and I’ve watched him get cuter and cuter with each passing movie, nearly all of which I’ve seen and loved. With the exception, of course, of Flipper (starring Paul Hogan?!) and the teen flicks he made in the late 90’s. I personally think The Ice Storm is his best, but Radio Flyer is one of my favorite movies of all.
I used to watch the Jon Stewart Show fairly regularly, then Jon Stewart disappeared for several years, to reemerge for the Daily Show.
Yeah, I think that’s the best I can do.
I remember Nicholas Cage from Fast Times at Ridgemont High and Valley Girl…but he has a famous uncle, I think, so does that really count? LOL
Ditto me on Tom Hanks from Bosom Buddies, and Ethan Hawke and River Phoenix from The Explorers (I actually have that on videotape, recorded from HBO!) I also remember Jason Alexander from the McDonald’s commercial. It was the McDLT, wasn’t it?
Jami Gertz and Sarah Jessica Parker from Square Pegs!
Courtney Cox from Family Ties and the Bruce Springsteen Video.
And don’t forget The Outsiders - the movie (filmed in Oklahoma, I might add…:)) that starred some now-famous guys when they were just getting their start: Patrick Swayze, C. Thomas (Tommy) Howell, Ralph Macchio, Rob Lowe, Emilio Estevez, and Tom Cruise. Also starred Matt Dillon, but I was already in love with him from My Bodyguard (also starring Joan Cusack and Adam Baldwin - no relation to the Baldwin brothers) and Little Darlings.
Ooooh, yikes, I think I’ll stop now.