You know that annoying friend who couldn't stop saying ''You look mahvelous'' back in the '80s? Well, if he suddenly starts screaming ''I'm jus' keeding!'' you can blame Fred Armisen. Just a few weeks into his first season as a featured player on ''Saturday Night Live,'' the 35-year-old former rock musician (he spent eight years behind post-punk band Trenchmouth's drum kit) is already cranking out catchphrases as the timbale-tapping Venezuelan ''nightclub comedian'' Fericito, an over-the-top blend of Tito Puente and ''The Simpsons''' Bumblebee Man.

Armisen's comedy career began almost by chance during the 1998 South by Southwest music conference in Austin, where he was a temporary drummer with the Waco Brothers. ''I really thought I was going to be bored,'' says Armisen. ''The daily seminars [are] just so laughably funny, I was like, 'I've gotta bring a camera and goof around with people.' I had no intention of turning it into anything big. I just wanted to make a tape.''

The resulting short film, ''Fred Armisen's Guide to Music and SXSW,'' features Armisen playing various unlikely interviewers (one deaf, one German, one a Hofstra University student) as they cluelessly quiz conference attendees like Janeane Garofalo and Pavement's Bob Nastanovich. ''I struggled so much being in a band,'' Armisen says. ''But as soon as I did this tape I got a piece written about me in the Chicago Reader.'' Word-of-mouth buzz earned him gigs screening the short as an opening act for rock bands. ''I'd get paid like $100 or $200, which was as much as with Trenchmouth. That's when it dawned on me: I don't have to load in all my drums. I just have to load in a videotape. There was no looking back.''

Doors flew open. An appearance at the Chicago Comedy Festival led to a recurring spot on ''Late Night With Conan O'Brien'' (as an amusingly unhelpful self-defense instructor); HBO tapped him as a correspondent for its ''Reverb'' music show; and Wilco's Jeff Tweedy asked Armisen to open some dates on an acoustic tour, which led to a funny cameo in the Wilco documentary ''I Am Trying to Break Your Heart.''

It didn't take long for ''SNL'' to call. ''At the risk of sounding corny, it's, like, the highest aspiration I've ever had,'' says Armisen. ''I've never felt so much like I'm putting my brain to good use.'' So will he have any pull when it comes to booking ''SNL'''s musical guests? ''Yes, I'm working on getting Shellac and the Mekons.'' Sorry, indie-rock fans: Jus' keeding.