Mike Tyson takes off the gloves in a new HBO documentary

LOS ANGELES – Mike Tyson is back in the ring, packing a completely different kind of punch.

In "Mike Tyson: Undisputed Truth," a one-man show premiering Saturday on HBO, the ex-champ is surprisingly light on his feet as he chronicles his life's journey from a hardscrabble childhood to his current state of tranquility.

Tyson may not be the next Laurence Olivier, but he gets points for his energetic commitment to a knockout script written by his wife, Kiki Tyson, and a rascally sense of humor, which includes a drop-dead hilarious impression of a white man's walk that conjures up the best of Richard Pryor.

"The similarity between boxing and acting is that I can't wait to get my hands on the guy, just like I can't wait to get onstage," Tyson said a week after taping the special. "The non-similarity is that I don't have to go to the hospital after I perform."

Reining in Tyson's antsy nature can be dangerous business, especially if the director is the comparatively diminutive Spike Lee.

"We'd have the music playing before the show and Mike's dancing and saying, 'Can we go, Spike?' " Lee said. "When he's in the wings and he's got his mic on, we'd have to hold him back until he heard the bell, because he's ready to go."

Lee got interested in the project after a friend caught one of Tyson's shows in Las Vegas. Once Lee came on board, he stripped the play of its singers and rock band, eventually taking the new version to Broadway. But this isn't "The Lion King."

"In no way am I Charlie Manson, but I'm never going to be Mother Teresa, either, OK?" he said in an interview. "Here's some good advice. Don't be so quick to understand me. Just don't get too close and be careful, because I will bite you."

That jokey reference to his infamous ear-chomping moment might not leave his old rival Evander Holyfield roaring with laughter, but Tyson gets away with it in front of a general audience. In their minds, apparently, the image of the scariest man to ever enter the ring has been replaced by that funny (though still scary) guy who was in "The Hangover."

Lee makes the case that Tyson is winning over people through brutal honesty.

"Most human beings are not going to display the dark parts of themselves, the demons they have, to the rest of the world. That's just not human instinct," he said. "When you see him on this stage naked, sharing his experience, his ups and downs, it's traumatic. He's not thinking about whether people are going to love me or hate me. He says, 'I'm going to tell you the truth. Do with it what you will.' It's the most courageous thing I've ever seen in my life."

Tyson describes the process a little differently. He has to step outside of himself when he's doing the play.

"I want to kill everybody in the room," he said. "With my performance, of course."

Neal.Justin@startribune.com 612-673-7431 • Twitter: @NealJustin