Hollywood clowns Will Ferrell and Mark Wahlberg are both known for their comedic performances in films like Anchorman and Ted respectively. Together, the actors have starred in three films now, including The Other Guys, Daddy's Home and now Daddy's Home 2, which has just been released in cinemas. You'd think after three films together – including all the hours in production, on set and doing the promotional laps around the world – they'd know each other pretty well by now. Turns out, they don't. The comedians appeared on Good Morning Britain last week and hosts Ben Shephard and Kate Garraway decided to do a little "how well do you know your co-star" quiz. [[instagramwidget||https://www.instagram.com/p/BbiwF19Bgse/?hl=en&taken-by=markwahlberg]] "We thought we'd have a little quiz to see how well you actually know each other," Shepard began. He started by asking how well the two friends knew each others' bodies. Shepard directed his first question at Wahlberg, asking him to pick an image of Ferrell's torso from four of his other co-stars. The former Marky Mark frontman showed no hesitation in picking the right answer. Next, Ferrell was hit with a question. "What do you know about Mark's body," Shepard asked. "Which of these statements is correct about Mark Wahlberg: he has a sixpack, he has a third nipple or he has 16-inch biceps." "Ah, six-pack – for sure. Biceps – yep," Ferrel said before pausing (for effect) and continuing: "Third nipple – I’m not aware of that." Wahlberg has been getting noticeably more buff lately, in preparation for a role in his upcoming action film Mile 22. [[instagramwidget||https://www.instagram.com/p/BbCQdcvhf6l/?hl=en&taken-by=markwahlberg]] But a third nipple? That wasn't something Ferrell had noticed before. "Is it true, do you have a third nipple?" the host asked, turning to Wahlberg. "It's true," he revealed with an abashed little smile. Ferrell – clearly baffled – looked around at the others to see their reactions while exclaiming a bemused "what?" The hosts laughed in their seats at Ferrell's visible surprise, Shepard asking: "How did you not know that? I thought you two were close?"

Wahlberg went on to explain that he'd "never made a point to show him." After a short while, Ferrell quipped: "I just assumed he has two of them."

Although Wahlberg didn't show his spare nipple to his co-star (or the camera), he did confirm that he's got one. But it doesn't come as a surprise really, as he's talked about it before and has bared it on the big screen in films like Shooter. It's been known for a number of years that Wahlberg has a third nipple, which he's described before as "the size of an infant's nipple". And he's not the only celebrity in the triple nipple club, with Tilda Swinton, Lily Allen and Harry Styles (who's actually got four) also known for having the abnormality. You can watch the interview here, and please do just for the look on Ferrell's face alone: [[youtubewidget||https://www.youtube.com/watch?v=wJh-jurxmGQ]] It seems like no matter how tight you are with someone, there's always something new the learn about them.

Mark Wahlberg reveals he has a third nipple to a speechless Will Ferrell