LOS ANGELES—Comic wildman Robin Williams left Entertainment Tonight reporter Maria Menounos in stitches Monday, cracking her up with a manic, off-the-cuff comedic riff covering everything from Survivor to Botox.

Robin Williams Leaves Entertainment Reporter In Stitches

"How does he come up with this stuff?" asked a still-laughing Menounos, who interviewed Williams as he arrived at the Regent Beverly Wilshire Hotel for a gala charity benefit for pediatric AIDS. "When Robin's around, you never know what he's going to say. But one thing's for sure: It's guaranteed to be funny."

Williams, 50, is renowned for his surreal, free-associative detours, which have delighted countless entertainment reporters on both coasts.

Williams went on the unexpected, wholly improvised comic tear when Menounos asked him about his outfit, a tuxedo accentuated by a pair of flashy, neon-purple cowboy boots. The query prompted Williams to launch into impersonations of a jive-talking black man and John Wayne before segueing into references to Joan Rivers, the reality-TV program Survivor, and the popular wrinkle remover Botox, leaving Menounos in what witnesses described as "hysterics."

"Yo, what is up, homeslice? Dis sucka be lookin' baaad tonight!" said Williams, showing off his outfit to Menounos. "Now listen, pilgrim, Monty Clift is down in Red River still lookin' for his boots. He's a little light in those loafers he's been wearin' lately, catch my drift? It's like Survivor: San Francisco... 'The tribe has spoken, and you look faaabulous!' Is Joan [Rivers] here tonight? Don't let her see me—her facelift stitches might pop out from the shock! Nurse, one million CCs of Botox, stat! No, we don't have time for the needle! Just back the truck up, fasten the hose, and pump it right into her skull! Boooop! Boooop! Boooop!"

Menounos responded to Williams with hearty laughter, eventually raising her hand in exhaustion and casting a "How does he come up with this stuff?" glance at the camera.

"It was classic Robin tonight," said fundraiser attendee Byron Allen, host of the recently cancelled junketainment program Kickin' It With Byron Allen. "He pulled it off so effortlessly, and fresh from his recent Grammy appearance, no less, when he held his award for Best Comedy Album against his crotch. Just another day at the office for this comic genius."

Access Hollywood anchor Pat O'Brien said that Williams, whom he has frequently interviewed over the past two decades, is remarkable for his outrageous unpredictability.

"When I interviewed him for Mrs. Doubtfire, I asked him if playing a woman came naturally," O'Brien said. "Although the question was posed seriously, I was kind of hoping it would set him up for a doozy of a spiel. And, boy, did it ever: Who knew he'd lisp in an effeminate voice, 'Why? What did you hear, Sweetcheeks?' and then, without warning, slip into a flawless impression of a televangelist exorcising a demon out of the lisping persona?"

"I love how, when he's conducting an imaginary exchange between two radically different personas—say, a flamboyantly gay hairdresser and a creepily placid children's-show host—he whips his head around, left and right," Access Hollywood reporter Billy Bush said. "It provides a helpful visual cue so you know when he's switching characters."

During a May 1992 press junket for the film Toys, Variety columnist Army Archerd had to be administered oxygen by paramedics after Williams overcame him with rapid-fire impressions of Jack Nicholson, a human beat box, and Ross Perot, squeezing in references to the savings-and-loan scandal and The Crying Game along the way.

"It was breathtaking to watch him weave all these seemingly unrelated pieces of pop culture into one side-splitting, completely ad-libbed routine," Extra host Leeza Gibbons said. "Robin's a national treasure."

Jules Asner, co-host of E! News Live, explained why Williams enjoys such a devoted following among entertainment journalists.

"It's true that Nathan Lane, Jim Carrey, and Carrot Top possess a certain hyperactive, spontaneous quality," Asner said. "Those guys are all incredibly zany and off-the-wall. But nobody goes off on a wild tangent quite like Robin. We just turn on the camera, ask a question, and let him rip. Do you know how much easier that makes our jobs?"

Asner said she "can't wait" for an upcoming interview with Williams for her Revealed series.

"What do you think he'll riff on instead of answering my questions?" Asner said. "Mike Tyson? Duct tape? Michael Jackson? Viagra? Monica Lewinsky? Enron? John Wayne Bobbitt? All seven? Lord, let it be all seven."