Ben Affleck’s BFF Matt Damon and The LEGO Batman Movie star Will Arnett were both guests on The Late Late Show with James Corden on Thursday, and Batman came up.

James Corden asked Matt Damon who his favorite Batman was… his friend Ben Affleck or Will Arnett, who was sitting right next to him on the couch. Damon dodged the question, and revealed that Arnett is actually Ben Affleck’s favorite Batman!

“I have it on good authority that Will is actually Ben’s favorite Batman,” Damon said. “We’re all fans of LEGO Batman. I went this last weekend with my kids. It’s just awesome.”

Damon then told a hilarious story about Affleck and his 4 year old son Sam. Sam thinks his dad really is Batman! So much so that he thinks the FedEx delivery guy is The Joker because of his purple uniform. Damon said that Affleck slipped the guy $20 to let them pretend fight, and that every time he comes by with a package he has to send him off in an aggressive way with his Batman voice.

It’s a hilarious story, check it all out in the video above!