Whether it’s on “Magnum, P.I.,” “Blue Bloods,” or “Three Men and a Baby,” Tom Selleck’s mustache is iconic. The thing has inspired countless articles on how to imitate it, and it has become synonymous with the 78-year-old actor. “Blue Bloods,” which Selleck stars in as Frank Reagan, just wouldn’t be the same without it.

But that has created some very particular problems for other actors on the show — namely Donnie Wahlberg, who plays Frank’s son Danny. While appearing on “The Late Show with Stephen Colbert,” Wahlberg revealed that he once attempted to wear a mustache on the series, only to be met with overwhelming indifference.

“My wife Jenny likes when I wear a mustache, so I wore one the whole summer hiatus, and my fans and my band and my kids were like, ‘Dad, you’re a creep. Get that off your face,’” he explained. “But my wife loves it, so she was like, ‘See if they’ll let you wear it on “Blue Bloods.”‘ So I called Leonard Goldberg, our executive producer, and I said, ‘Hey, I was thinking of wearing a mustache … And it was crickets on the other end of the phone. It was crickets.”

But according to Wahlberg, Selleck doesn’t always enjoy wearing his own mustache. In fact, he’s not even as big a diva as the mustache itself.

Selleck is apparently a great guy, despite his demanding ‘stache

“Seriously, Tom [Selleck] doesn’t always love the mustache,” explained Wahlberg, before describing Selleck as a decent guy both on and off the “Blue Bloods” set. “He’s been so good to me as a younger guy coming on the show,” Wahlberg shared.

But that didn’t stop Wahlberg and Colbert from joking about the massive ‘stache and characterizing it as a diva with its own trailer. “We’re not technically allowed to look at the mustache,” revealed Wahlberg, playing along. Wahlberg also claimed that the mustache texted him only minutes after he had asked his executive producer about wearing his own ‘stache on his show. The text? “Back off.”

Neither man revealed whether Selleck’s mustache — which he once shaved, memorably, on “Late Night with Conan O’Brien” — is a Method mustache as well, refusing to speak to other mustaches on set. So, any fans who are now debating whether the mustache is truly a diva will just have to keep on wondering.