Justin Bieber is challenging Tom Cruise to an MMA fight.

Warner Bros.

I know, I thought it was garbage too until I pulled up his tweet from yesterday.  Is he crazy?  He couldn't beat Tom Cruise in a 50 yard dash so what makes him think he could beat him in the octagon.  This just goes to show that the kid hasn't grown up and is still cocky Bieber thinking he is invincible. That's just my opinion though.  I would LOVE to see Tom take him in the ring and show him whats what.  So far he hasn't responded to Justin's laughable challenge.  I'm betting Tom is a little busy right now shooting a movie over seas, maybe climbing the side of a cliff perfecting his stunt scenes.  Justin has a LOT of time on his hands these days.  From the look of his Instagram feed, he spends most days lying around his pool petting his puppy and new wife Hailey Baldwin.

After Bieber's tweet, Conor McGregor chimed in...