Justin Bieber teases older Ashton

Justin Bieber makes Ashton Kutcher feel old.

Justin, 18, poked fun at the actor as they appeared on US TV show Jimmy Kimmel Live on Tuesday night. The interview comes ahead of their episode on Ashton's celebrity prank show Punk'd. When asked if he was old enough to watch the show when it first came out, Justin said in tongue-in-cheek that he was only "three or four".

The 34-year-old actor then laughed and walked around like an old man in response to the Canadian star's jibe. Justin also made fun of Ashton when questioned about whether he considered the Two and a Half Men star a role model.

"Um, this guy a role model?" he teased. "Definitely for this Punk'd thing [that] we're doing, he's the master at it so I'm looking up to him as far as that."

Justin adds he has always been a prankster and had fun filming the comedy TV show.

The singer, who recently released his single Boyfriend, earlier tweeted about their appearance on the show.

"...gonna head to @jimmykimmeltonight to hang with @aplusk and talk punk'd and #BOYFRIEND," he wrote.

Ashton also promoted their interview on his Twitter page alongside a photograph of himself with Justin. "On @jimmykimmel tonight with jb and this guy, Bieber," he wrote.