Fergie's husband showed up on Friday's Halloween episode dressed as Lloyd Christmas from Dumb and Dumber, and felt pretty silly when a man jumped out at him while he was talking about his new movie, Lost In the Sun.
"Son of a b**ch!" he exclaimed before letting out a laugh.
Duhamel and Fergie are big fans of Halloween and so is their son Axl.
"He knows what Halloween is and he loves watching his Halloween videos. It's not just five little monkeys jumping on the bed, now it's five little zombies jumping on the bed," the 42-year-old actor told ET. "The big question is whether or not he's going to be a construction worker or a Teenage Mutant Ninja Turtle."