Niall Horan Tattoo Prank [PHOTO]: One Direction Heartthrob Gets James Corden's Face Temporarily Inked on Butt, Moons Crowd in Calvin Klein Boxer Briefs

One Direction heartthrob Niall Horan recently debuted his "new tattoo" to a shocked crowd of fans on the hit British game show "A League of Their Own." The 1D crooner mooned the audience and revealed a portrait of host James Corden's face tattooed on his BUTT! But no worries, the bizarre tattoo was only temporary... although it took poor Horan over three weeks to fully remove!

Horan is the only One Direction boy who doesn't flaunt any body art - but that all changed on a recent episode of Sky 1's comedy show "A League of Their Own." Check out a photo of the ridiculous ink here... although Horan's derriere looks quite adorable in those Calvin Klein boxer briefs!

According to game show host James Corden:

"We made a thing on the show that he's the only member of the band without a tattoo. I said to him we've got this idea of putting a tattoo of my face on your body. Niall went, 'You should put it on my ar*e!' We tattooed it on to his left buttock - it took him three weeks to get rid of it. He sent me updates every week, with a photo of my fading face on his a*se saying, 'It's still not gone yet.'"

Funny stuff!

Despite the tattoo prank, Horan DOES NOT plan on getting inked like his fellow bandmates anytime soon.