Yesterday Twitter’s Biz Stone, who has been all over the U.S. the past couple of weeks, was a guest on Howard Stern’s radio show.

Stone was unusually open in his interview with Stern, who kept pushing once he started getting results, and of particular interest was Biz provided greater detail on why he and Evan Williams turned down that $500 million buyout offer from Facebook in 2008, and what it was like to meet – and be proposed to – by ‘ the great Mark Zuckerberg’.

Details courtesy of AFP:

Williams and Stone made a road trip from San Francisco to Facebook headquarters in the Silicon Valley city of Palo Alto to meet with Zuckerberg in late 2008.

On the way Williams and Stone pondered a price for Twitter, and settled on a figure of $500 million tossed out by Stone.

Zuckerberg led Williams and Stone into a room and sat in the only single chair, leaving the Twitter co-founders to share a small love seat.

“It was fun, but it was also awkward,” Stone said of the chat with Zuckerberg. “I was making all these jokes, and they were just dying.”

Zuckerberg asked the pair to propose a sale price for Twitter, and responded “That’s a big number” after Williams tossed out the $500 million figure, according to Stone.

Facebook made a cash-and-stock offer for Twitter during a cordial meeting that included lunch, Stone said.

“When talking to him it was weird,” Stone said of Zuckerberg. “He was one guy but it almost seemed he had 12 people in his head,” he added during the Stern broadcast. “He had already gone through every possible scenario that we could talk about.”

After returning to Twitter offices that afternoon, Williams sent Zuckerberg an email saying the firm wasn’t for sale.

“To be perfectly honest, we really had no intention of selling,” Stone said. “We just had to go meet the great Mark Zuckerberg.”

You can listen to the full, 45-minute interview here.

Stone also stated that Twitter needs to add functionality to their still fairly-unpopular internal retweet system so that people can comments. If true, that’s pretty huge.

An additional highlight included Biz fast-tracking the verification of Stern crew-member Ronnie The Limo Driver.

Well – so he said. Ronnie still doesn’t have his badge, but I guess like most things Twitter, it’s coming. Eventually.

(Sources: AllThingsD, AFP.)