Kate Walsh a surprise at Charlie Sheen's roast

LOS ANGELES, CA - SEPTEMBER 10: Actress Kate Walsh speaks onstage at Comedy Central's Roast of Charlie Sheen held at Sony Studios on September 10, 2011 in Los Angeles, California. (Photo by Christopher Polk/Getty Images)
Christopher Polk
Kate Walsh at the "Comedy Central Roast of Charlie Sheen," Sept. 10, 2011, in Los Angeles.

(CBS) Anyone tuning into "The Comedy Central Roast of Charlie Sheen" was likely surprised to "Private Practice" star Kate Walsh on the stage. As host Seth MacFarlane said several times, "What are you doing here?"

Pictures: Charlie Sheen
Pictures: Kate Walsh

Walsh was there to skewer Sheen along with everyone else. She told USA Today, "[I]t was a good exercise in masochism to come up here." Walsh told the paper she got her career start in improv comedy.

"You never want to rest on your laurels. You want to keep doing things that terrify you," she told USA Today.

Other highlights - or lowlights, depending on your point of view - included host MacFarlane's opening with an Amy Winehouse joke and William Shatner telling Charlie Sheen how he used his warlock powers to turn a kidney stone into a house for Habit for Humanity. Would any of these gags fly at the Dean martin Roast of Bob Hope?

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