Stars in Skivvies: The Sexiest Underwear Ads Ever

Not that we really needed an excuse to look at these hot celebs in their unmentionables, but this week marks the 20th anniversary of Mark Wahlberg's iconic strip-down for Calvin Klein so we had an extra-good reason

KELLAN LUTZ

"What more can you do than be on a billboard for something that you grew up thinking was super sexy and classy?" Kellan told PEOPLE of his 2010 ad, paying homage to the brand and the man who dropped trou 18 years earlier.