Singer Justin Bieber.
Singer Justin Bieber.

Justin Bieber and Lady Gaga are set to play aliens in the yet to be released sci-fi comedy Men in Black III.

In an interview to Collider, the film's director Barry Sonnenfeld confirmed that both the pop stars will play small roles in the movie which also features actors Will Smith and Tomme Lee Jones reprising their earlier roles of alien combatants, Agent J and Agent K, respectively.

"In this [installment] there are a few people that you'll see up on the surveillance board, including Lady Gaga, Tim Burton, who probably knows more about aliens than I do, and let's see who else... Justin Bieber," Sonnenfeld said. "The challenge is getting celebrities that are famous, will give you permission and won't be like 'Who's that guy?' in 10 years," Sonnenfeld told Collider.

The singers are not the first people to do a guest role in the hit film series. The first installment had a big star cast including Steven Spielberg, Danny DeVito, George Lucas, Sylvester Stallone and Isaac Mizrahi playing small guest roles whereas the second installment had Michael Jackson playing a cameo as Agent M.

Asked if he uses the ultimate weapon (Will Smith) to sign the famous celebrities for his movies, Sonnenfeld admitted as much but immediately added that he does not like to use that weapon too often.

"You know we don't like to use that weapon too often. The hard part is really figuring out the combination of who won't be "who's that person" in 10 years. But so far we've been pretty lucky and people have been kind and interested. I am surprised that Lady Gaga said yes," he is quoted as saying.

Earlier this year Will Smith hinted about Lady Gaga's cameo in MIB III in an interview to Brazilian website El Corillo RD, reported entertainmentwise.

"We must keep as a surprise that Lady Gaga appears," he told the website.

The movie will release in theatres on 25 May.