Jaleel White (Steve Urkel, "Family Matters")
Then: "Family Matters"' nasal-voiced, robot-doppelganger-creating nerd was so popular, it's easy to forget that the character originally wasn't intended to last more than a single episode. But his instant popularity made Urkel the breakout star of the "Perfect Strangers" spin-off, inspiring a catchphrase ("Did I do that?"), breakfast cereal (Urkel-Os), novelty dance and much more. Even Steve's suave alter ego Stefan Urquelle got more screen time than 80 percent of the "Family Matters" cast.
Now: After popping up as Urkel on "Full House," "Step by Step" and "Meego," White made various attempts to return to television with mixed results. (His most stable role has been as voice of Sonic the Hedgehog.) Recently, White turned screenwriter with the upcoming "Did U Get My Text," and spent a wild night drinking with Charles Barkley, resulting in the baller getting popped for a DUI.
Anthony Michael Hall ("Weird Science," "Sixteen Candles")
Then: Those two flicks plus "The Breakfast Club" cemented Hall's geek cred during the early '80s, a persona he attempted to shed during his single season on "Saturday Night Live." If there was a scrawny teen during the '80s, Hall played him.
Now: Hall eventually outgrew his awkward phase, and actually went on to play jocks in "Johnny Be Good" and "Edward Scissorhands." He also spent several seasons on USA's "The Dead Zone" and recently turned up as a newscaster terrorized by the Joker in "The Dark Knight." The Hall of today is, dare we say it, kind of edgy. We'd love to see him return for a "Breakfast Club" reunion and kick Judd Nelson's paunchy ass.
Neil Patrick Harris ("Doogie Howser, M.D.")
Then: For four seasons on ABC, Harris defined overachiever as child prodigy Doogie, the only 16-year-old who knows how to perform a tracheotomy.
Now: Post-"Doogie," Harris went on to conquer film ("Starship Troopers," "Harold and Kumar"), TV (alpha-male Barney's quips are easily the best thing about "How I Met Your Mother") and even the Web ( "Dr. Horrible's Singalong Blog"). Now whatever happened to Doogie's girlfriend, Wanda?
Paul Reubens (Pee Wee Herman)
Then: With his signature gray suit and red bowtie, Pee Wee Herman defined '80s nerd chic and delighted kids with films ("Pee Wee's Big Adventure," "Big Top Pee Wee") and a cutting-edge TV series ("Pee Wee's Playhouse.")
Now: After some unfortunate legal trouble in the '90s (Pee Wee and adult movies don't mix), Reubens bounced back with memorable film and TV appearances ("Blow," "Pushing Daisies"). And after a 15-year hiatus, Pee Wee returned in 2007 at the Spike TV Guy's Choice Awards. Rumor has it Reubens plans to bring back Pee Wee in two films: a "Pee Wee's Playhouse" reunion aimed at a younger audience and a decidedly darker take for adults (supposedly written as a Johnny Depp vehicle.)
Dustin Diamond ("Saved by the Bell")
Then: When Samuel "Screech" Powers first appeared on the short-lived NBC sitcom "Good Morning Miss Bliss," no one could have guessed he would go on to be one of TV's most beloved nerds. After "Miss Bliss" was reformatted into the long-running "Saved by the Bell," Diamond played the character for a whopping 13 years in all of the hit show's various incarnations.
Now: Diamond has enjoyed a healthy reality-TV career of late, appearing in "Celebrity Boxing" and "Celebrity Fit Club," among others. He's also had his share of former child-star mishaps, nearly losing his home to debt and appearing in an unfortunate sex tape titled "Saved by the Smell." (The less said the better.) Lately he's been threatening to pen a "Saved by the Bell" tell-all, finally giving the world the Lark Voorhies dirt it so desperately craves.