On Sunday night, the world-famous superstar challenged A-list actor Tom Cruise to a "fight in the octagon" — a UFC-style battle — for no apparent reason.

"I wanna challenge Tom Cruise to fight in the octagon. Tom if you dont take this fight your [sic] scared and you will never live it down. Who is willing to put on the fight? @danawhite?" tweeted Bieber.

(Dana White is the current president of the UFC, and as of this writing, he has not replied to Bieber's tweet.)

UFC champ Conor McGregor chimed in after Bieber's challenge, saying that if Cruise is "man" enough to face off with Bieber, his McGregor Sports and Entertainment would host the bout.

McGregor also offered to fight actor Mark Wahlberg, after asking if Cruise had "the sprouts to fight."