That '70s Show may have ended over a decade ago, but Ashton Kutcher [1]'s retro mustache suggests otherwise. In a recent appearance on The Tonight Show Starring Jimmy Fallon [2], the actor shared the star-studded story behind his new facial hair. In summary: Adele and Mila Kunis [3] are to blame.

"I never intended to have this. I don't think I look good with it, but I'm keeping it," Kutcher said before explaining how he had shaved his beard down into a mustache solely for Adele's 1970s-themed birthday party earlier this year. If you refer to photos from said birthday party [4], however, you'll see how the theme was actually inspired by the 1930s. Kutcher only realised that after already arriving — dressed in a vest, boots, and bell bottoms.

Months later, Kutcher has decided to keep the mustache to get back at Kunis, who evidently relayed the wrong party theme. "This is payback," Kutcher added. "It's a full-blown spite stache, and now she likes it, so now I can't get rid of it." Watch him tell the unfortunate series of events above.