AGES Zach Braff, 26; Sarah Chalke, 24; Donald Faison, 27; Judy Reyes, 33 MOMENT OF ARRIVAL As the overworked young medical staff on the hit freshman comedy Scrubs, they've kept viewers in stitches -- and emerged as NBC's most promising new ensemble since Friends and ER in 1994. PREVIOUS JOBS Braff played Woody Allen and Diane Keaton's son in 1993's Manhattan Murder Mystery (''When I look at that scene now, all I can see is the terror in my eyes''). Chalke replaced Lecy Goranson as elder daughter Becky on Roseanne from 1993 to '97. Faison costarred in the Clueless movie and TV series (''For a while, I was called Clueless -- if I went to the 'hood, it was 'Yo, Clueless!'''). Reyes recurred as a prison guard's wife on HBO's Oz but ''he got his eyes gouged out, so I don't know if they're going to bring him back.'' WHAT FAME HAS BROUGHT A ride on a float in Macy's Thanksgiving Day Parade. ''It was totally surreal to be paddling a canoe with Pocahontas,'' says Chalke. ''The thing we heard most being screamed out was, 'Oh my God, it's the guy from Clueless!''' WHAT'S NEXT Finishing Scrubs' first season; Faison plays a limo driver who seeks revenge against a piggish movie producer (Paul Giamatti) in Universal's Big Fat Liar, due in February. ''I did it because I thought the strike was going to 'F' everything up, and I was gonna go broke. But dude, the movie is so hilarious!''