Late-night host Conan O’Brien Tuesday called Robin Williams “the best talk show guest in the world,” and he was probably right.

Williams, who died Monday at age 63 in a suspected suicide, brimmed with a manic, frenetic energy, buzzing from one impersonation to the next. Talk to Williams, and you might as well be talking to 18 different people at once.

Robin Williams, in the Moment

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While Williams found success as a sitcom and movie star, his roots were forged in comedy, with his improvisational humor bringing a madcap edge to his performances. It was fun to watch Williams ad-lib on late-night TV as he rattled through topical issues, impersonations, off-color riffs and songs. He always brought full-octane to his appearances, connecting beyond simply plugging his latest project.

As a result, Williams’ death was felt particularly hard on late-night television. While the late-night tributes are still rolling in – some shows are in re-runs this week – three shows celebrated Williams’ life during Tuesday’s episodes: “Conan,” “Tonight Show” and “Late Night.”

A Colorful Bike, a Colorful Man

A few years ago, O’Brien was going through “a bump in the road,” as he describes it.

Out of the blue, Williams bought him a bicycle.

“He was the first person to buy me a bicycle since my parents bought me a bicycle,” O’Brien said on his TBS show Tuesday, one day after he broke the news of Williams’ death to his audience.

Williams wasn’t a standard, typical sort of person, so he didn’t buy O’Brien a standard, typical bike. Instead, the bike was bright orange and green with shamrocks on it. O’Brien called Williams to thank him.

“Robin, I’m floored by this bike,” O’Brien said.

“I knew you ride, I knew you could use it,” Williams responded. “Does it look ridiculous? Does it really look ridiculous?”

“Yeah, it looks ridiculous.”

“Good. Do you really look stupid riding it?”

“Yeah, I’m gonna look really stupid.”

“Well then that’s good then.”

O’Brien thought about the bike this week.

“He had that amazing spirit and fun, the generosity, but also the fun at the same time. And so often I’d look at that silly bike and think, what a wonderful spirit. What an amazing spirit,” O’Brien said. “And we know now that he had his battles, he had his … and I think it’s very courageous. I think it’s particularly courageous for someone to be that generous of spirit in the face of that kind of depression.

“Such a lovely, special man.”

‘The Muhammad Ali of Comedy’

Jimmy Fallon, the “Tonight Show” host, choked back tears as he discussed the death of one of his comedic idols.

“He was one of a kind, he was one in a million,” Fallon said.

Fallon has been imitating Williams, mimicking his constant movement and miles-a-minute banter, since his “Saturday Night Live” days. That portrayal was on display Tuesday, with Fallon busting into his best Williams impression one more time, an impersonation of the great impersonator.

“He was the Muhammad Ali of comedy,” Fallon said.

Fallon introduced a clip from Williams’ first “Tonight Show” appearance from 1981. And then Fallon stood on his desk, calling back to Williams’ performance as professor John Keating in “Dead Poets Society.”

“Oh captain! My captain! You will be missed,” he said.

Awash in the Spotlight

Williams’ first “Tonight Show” appearance came in Oct. 14, 1981.

By then he was a star, with “Mork and Mindy” a household hit. His film “The World According to Garp” hadn’t been released yet.

“He doesn’t do many outside appearances,” host Johnny Carson quipped.

Carson and Williams discussed stage fright.

“I suffer from severe dyslexia, too,” Williams said. “I was the only child on my block on Halloween to go ‘trick or trout’ … Here comes that young Williams boy. Better get some fish.”

“Where is home for you? Or did you come from a home?” Carson asked.

Williams waved and pretended to wear an imaginary strait-jacket before hopping out of his chair to speak into the boom microphone.

Then he drank out of Carson’s coffee mug.

“Don’t be afraid. The sores went away,” Williams said.

Later, Williams slinked off from the set, walking into the crowd, gesturing to attendees, awash in the studio spotlight. He sprinted past the camera, zipping about, dancing in and out of frame.

Guideposts for Growth

Seth Meyers worked at a video store as a teenager, and he was always taking out Williams’ stand-up specials.

Movies such as “Dead Poets Society” and “Good Will Hunting” served as guideposts for the “Late Night” host, reflecting moments in his own maturity.

Meyers hopes we can learn from Williams’ battle with depression.

“If there’s anything we can do to honor his memory, I would hope it would be to use this opportunity to educate us more about this terrible affliction,” Meyers said during Tuesday’s episode.

“So we just want to say that we miss Robin, but we’re also very lucky to have had him at all.”