The hip-hop mogul stunned the studio audience watching The Chris Gethard Show when he made full use of a so-called "Diddy Door", designed specifically for the star.

Host Gethard installed the funny feature in a bid to convince Diddy to feature on the show, and The Office comedian even sent the rapper a special key so that only he could unlock the set entrance.

Gethard's dreams came true on Wednesday when Diddy burst onto the set via his own door, appearing in a puff of smoke.

During his unexpected appearance, Gethard took a call from a viewer named Zach, who turned out to be The Hangover star Galifianakis, who serves as an executive producer on the show.

Claiming to be calling in to "save" the show, Diddy told Gethard, "Let him know the show has already been saved."

As Galifianakis pretended to wonder "Who's that?", Diddy responded by using the old Batman TV theme song as he declared, "Blackman is here! It's BLACKMAN!"

The two subsequently became engaged in a little light-hearted sparring as Diddy chastised Galifianakis for trying to interrupt him.

"Zach, no one interrupts Blackman saving the day!" he exclaimed.

The stars then make arrangements to battle it out in person, with Diddy saying, "I'll meet you in Kansas City tomorrow at 4pm!," as he vowed to take Galifianakis down.