Faster than a speeding Robin Williams, a quartet of brainy clowns called the Firesign Theatre erupted from hippiedom 25 years ago. Its first 10 records sold a then-impressive 1.5 million copies and became a staple of underground radio and campus parties. Firesign routines, notably ''We're All Bozos on This Bus,'' are a happy (if hazy) memory for the generation that inhaled. In 1987, Garrison Keillor explained that he was moving to Denmark so he could be ''just another bozo on the bus.'' With its radio-based constituency waning, however, the group was dumped by its record label in 1976 and wandered on to solo projects; eventually the Firesigners stopped performing together in 1981.
Phil Proctor, 52, Peter Bergman, 53, Phil Austin, 51, and David Ossman, 56, celebrated their 25th anniversary April 24 with a reunion show at Seattle's 2,900-seat Paramount Theater, far from the media glare of Hollywood. The sold-out crowd at the ''Illusion of Unity'' show included Microsoft cofounder Paul Allen and members of Pearl Jam, Heart, and the Flying Karamazov Brothers. ''It was like a higher-grade version of The Rocky Horror Picture Show,'' said Microsoft's Nils Von Veh. Fans shouted along with the dialogue of beloved routines like ''Nick Danger, Private Eye.''
And the Firesign whimsy is charming a whole new generation. ''We played Don't Crush That Dwarf, Hand Me the Pliers on the Lollapalooza bus last summer,'' said Pearl Jam drummer Dave Abbruzzese, 24. ''It's the wittiest political satire I ever came across.'' Seattle resident Harry Anderson of Night Court marveled after the show: ''A guy in front of me had his 9-year-old along, as if to say, 'This was my generation's Ren & Stimpy.'''
In fact, Firesign Theatre may soon join Ren and Stimpy on TV. ''Illusion'' organizer Richard Baker, who manages Home Improvement's Tim Allen, is hoping to produce a cable special. Steve Allen will host a Firesign documentary this fall on American Public Radio, and it was even approached by Lollapalooza '93.
Unlike such later comedy revolutionaries as Saturday Night Live and Steve Martin, Firesign Theatre depended on radio, and as formats became more rigid, their free-flowing comedy found itself with no outlet. But each member has been doing well on his own: In L.A., Bergman produces radio campaigns for movies (Wayne's World, Dave), and Proctor does voices for Smurfs and Rug Rats. On Whidbey Island near Seattle, Ossman produces such public-radio specials as 1988's War of the Worlds anniversary remake. Austin, who lives on nearby Fox Island, is talking to Chevy Chase about working on his Fox-TV talk show this fall.
But the soloists clearly crave the quartet. On Proctor's answering machine, Nick Danger's nemesis, Rocky Rococo, menacingly makes this solemn announcement: ''We're ba-ack!''