Channing Tatum is shedding that Sexiest Man Alive image for a good cause.

To kick off the Magic Mike XXL charity campaign he's spearheading with Omaze, which allows one fan the opportunity to be part of his entourage at the movie's hip shaking L.A. premiere and afterparty, he underwent a major makeunder. The 35-year-old actor went undercover — as "the most terrifying marketing exec ever" — at a test screening of the movie and gave Yahoo the scoop on his big-hearted prank.

So what was it like for Tatum to be unsexy for a day? "I thought he was very sexy personally," he laughs while talking about his follically-challenged counterpart, Scott. "Why wouldn't you want to just change it up every once in a while and get a different flavor?" He continues, "I really enjoy that stuff. I'd go around in a costume every day if I could for no other reason other than all bets are off. You don't have to be responsible and you can do whatever you like, especially as an older person. No one ever says anything if you're slightly older and saying weird stuff to people."

For his undercover escapades, he interviewed unsuspecting fans about everything from "pelvic thrusting" to their favorite actor in the film. One woman looked Tatum, dressed as "Scott," in the eye and told him that Matthew McConaughey was her favorite actor in the original 2012 film.

"It was awesome," he says of his co-star and fellow Sexiest Man Alive being the preferred choice. "That is what we were looking for. It's hilarious to me. I just went, 'Yes.'"

Equally as cute is an older woman fanning herself after watching Tatum unmask himself and twerk along with some other ab fab male dancers.

"Oh my god — rewatch the video," Tatum says. "Keep watching all the people's faces. Each one of them is such a nice little meal. Go down the line and watch everybody's face."

The winner of the fundraising campaign gets to ride to the premiere with Tatum in his motorcade after getting primped at a spa, set up with a tux or gown, and being put up at a four-star hotel. So what makes him a good date?

"I'm going to be feeling really, really good that night," Jenna Dewan's husband promises. "It's going to be a ridiculously fun time. We make these movies in such good spirit and all the people we get to do it are so much fun… The [sequel] is so much more fun. Not that the first one wasn't its own slice of fun. But we had to go a little darker with this to prove we know what the world was. It's a different movie. We really wanted to take the gloves off with the second one. You can't give [fans] the same thing."

Tatum says there's a good chance there will be dancing — and other fun — after the afterparty.

"It's a large possibility," says Tatum, whose fine dance skills we first saw in Step Up are on display in the video as he does some "man twerking" — or, as he dubs it, "merking."

The contest winner isn't the only beneficiary of Tatum's Omaze campaign. The donations (it's $10 for each chance to win) go to support the Runa Foundation, which is something close to Tatum's heart. He became involved with the non-profit, which looks for new ways to value tropical forests that can support local livelihoods and conserve forest ecosystems, following a trip to Ecuador to meet the Kichwa and Sapara tribes in Ecuador. The organization is now working to set up two facilities where research can be done in conjunction with the tribes.

"The clinics will be the first time really that western medicine has really studied tribal medicine," says Tatum, who adds, "We are really, really excited that they would like to share their knowledge with us… It's not that much money to set up a facility that could possibly have unending, pure, unbelievable opportunity for helping and healing."

To enter for a chance to shake it with Channing at the premiere of Magic Mike XXL, visit Omaze.