AS DIFFICULT AS THE FIRST WEEKS were for Conan O'Brien after he took over NBC's Late Night as David Letter man's successor last year, they may have been even tougher for sidekick Andy Richter. For better or worse, this was Conan's moment—he had to be taken seriously. Richter was...well, who was this big lug, and why was he sitting on the end of the couch? USA Today's Matt Roush, for one, suggested that Richter was ballast and ought to be dumped.

What a difference 14 months make. O'Brien now seems more relaxed in his role, Late Night's ratings are up, and Richter, 28, has become, almost inexplicably, the object of late-night idol worship. Or is it idle worship? Though fans sometimes chant "And-y! And-!" during commercial breaks, Richter doesn't really do all that much. Mostly he's sort of a postmodern Ed McMahon: he laughs at O'Brien's jokes and helps out with skits but is simultaneously aware of the role's showbiz hokiness. He's in on the joke. As Richter puts it, "Conan has to be the host, but I have more leeway. I can be the smart-alecky curmudgeon, the dim-witted man-child or the naive audience surrogate." Or he can just be, and often is, the guy on the end of the couch.

When he is activated, Richter's best moments are often in sketches (he played both Roseanne and Tom Arnold in one) or giving his Andy-was-there reports. At the Miss America Pageant he urged Miss New Hampshire to reveal which contestant had the ugliest feet (Miss Massachusetts); during a Disney World segment he leaped on a bench, yelling, "Eeek, a mouse!" at the approach of Mickey. "We have to be more ambitious than past talk shows," he says. "People aren't so fascinated anymore by what Gina Lollobrigida has to say about working with Charlton Heston."

That attitude and his forays out of the studio are just fine by his boss. "There are no rules for this job," says O'Brien. "We call Andy a sidekick, but he's really just a funny guy who happens to be sitting on the couch."

Richter knows sofas. The second of four siblings, he spent hours on one in front of the TV while growing up in Yorkville, Ill., outside Chicago. He studied film at Columbia College in Chicago but left six credits shy of graduation to work in production on commercials. Bored with the job and still living at home with his mother, Glenda, a cabinet designer (his parents divorced when he was 4; his father, Larry, teaches Russian at Indiana University), Richter began performing with local improv groups and found himself "meeting some of the funniest, most interesting people I'd ever met," he says. Richter made his TV debut in 1991 as a victim of serial killer John Wayne Gacy in a Hard Copy reenactment. "I was just happy to get paid for a job," he says, "even if I had to die in the process."

After gathering further stage experience as Mike Brady in the Off-Broadway and Los Angeles productions of The Real Live Brady Bunch, Richter and others from the cast were asked by MTV to develop a sketch comedy show. "It wasn't quite right for MTV" he says of the failed effort. "I think we were all a little too fat. In MTV terms, we were like Thanksgiving Day balloons."

Luckily though, Richter landed on the new Late Night as a writer. Before the show even premiered, producer Robert Smigel had promoted Richter to being O'Brien's sidekick. "I didn't want a yes-man," says Smigel. "I wanted Conanto have someone to bounce off of. Andy's likable and the perfect contrast."

When he's not at the show's Rockefeller Center studio or in his office there ("I have Letterman's ashtray," he boasts), Richter is either auditioning for voice-over work ("They say, 'We want you to sound like the person from Northern Exposure,' so I try to sound like Janine Turner") or at home in his Manhattan loft with his wife, actress-writer Sarah Thyre, 26, on their new Ralph Lauren sofa. They met in Chicago, began dating in L.A. while costar-ring in The Brady Bunch, and they wed last March. "She's one of the forces keeping me happy," says Richter. "She helps me remember that the important thing in my life is going home."

Right now, between his life at home and on Late Night, Richter says he's one contented couch potato. "I don't really want to be a star," he says. "I have an ego, but it's a pretty sedate one. I'm just happy to be here and lucky to have a job I don't have to die for."