Will Ferrell stars in his 2009 one-man show, "You're Welcome America. A Final Night with George W. Bush." (Robert J. Saferstein/Jeffery Richards Associates/AP)

Besides '70s-style "Anchorman" Ron Burgundy, one of the characters comedian Will Ferrell is known for is his spot-on George W. Bush that he portrayed throughout his "Saturday Night Live" career. But that casting was more of a happy accident, Ferrell revealed Tuesday night at the Newseum in Washington, in one of his rare recent appearances where the actor wasn't dressed like the vintage newsman.

"I just kind of stumbled into doing them," Ferrell said of impressions generally. "And the only time I did someone who was pretty much in the mainstream happened by mistake and that was President Bush." Ferrell explained that his "SNL" colleague, Darrell Hammond, "already had Al Gore down."

Leading up to the 2000 election, "SNL" executive producer Lorne Michaels asked Ferrell if he might want to play Bush. "Do you want to play Bush? You're tall, he's tall," Ferrell recalled Michaels saying. "Why not, he's not going to win," Ferrell replied back. (Eight years later, Ferrell's Bush was still going strong.)

The "Anchorman 2" star also explained how he was able to pull off Dubya. "I just find one thing I can hang my hat on, and for Bush, for instance, I just knew he squinted his eyes a lot ... and then I got more comfortable with the voice," Ferrell said. "And so if you could find one little tick you can build it."

The comedian said he generally liked to stay away from mainstream characters, opting for the more bizarre. "I always had just weird eccentric ideas of impersonating people that no one would necessarily think about," he said. "You know, obviously 'Saturday Night Live,' the stock and trade is political impersonations and I thought, no one's ever impersonating Janet Reno – that's someone who needs some attention."

From that thought, Ferrell came up with Janet Reno's Dance Party, mocking the Clinton-era attorney general. The skit quickly became a hit, with the real Janet Reno even making a cameo in the last one of those parties. "She felt like what we do on the show is such a healthy part of the Democratic process," Ferrell said. "You have to be able to feel free to make fun of your leaders."

Ferrell was in Washington to tour "Anchorman: The Exhibit," at Washington's museum of news in advance of the "Anchorman 2" release on Dec. 18.