Mila Kunis pranked Ashton Kutcher into growing a mustache for Adele’s birthday party which she told him was ’70s themed — so he’s keeping it out of spite

Ashton Kutcher has told the hilarious story behind his current facial hair on “The Tonight Show Starring Jimmy Fallon” on Monday.

The actor is sporting a mustache, and it turns out he was pranked into growing it by his wife Mila Kunis.

Kutcher told Fallon that he’s now keeping it out of spite.

It all started when the A-list couple were getting ready to attend Adele’s birthday party.

On the day of the event, Kunis told her husband the party’s theme was “1970s New Year’s.”

“I’m like, ‘Who the f— throws a 1970s New Year’s birthday party?!'” Kutcher said.

But he put the effort in, donning bell-bottomed pants, boots, a vest, and a scarf tied around the neck.

“I’m looking in the mirror and I’ve got a beard going and I’m like, ‘Oh, I’m going ’70s ‘stache,'” Kutcher told Fallon.

“It’s thin, it’s like a high school boy trying to grow a mustache, but it looks great for the party.”

With Kunis wearing what her husband called a “timeless jumper that could be from any era,” the couple arrived at the party.

And it was only when they got there that Kutcher realized his wife had got one over on him.

“We show up, and I’m looking around, and no one else is in 1970s anything,” he said.

“The theme for the party is 1930s New Year’s! And I look like Burt Reynolds from ‘Boogie Nights,’ and I’m like, ‘This is a joke!'”

Kutcher said he was “just playing it off like this is how I’m doing it these days.”

“And I’m like, ‘Yeah, what’s up, Jay-Z? Yeah, this is my thing now,'” he continued. “And it was really awkward.”

But Kutcher says he’s now keeping the “spite stache.”

“I never intended to have this, I don’t think I look good with it, but I’m keeping it,” he said.

“I feel like a baron.”