It's always a good idea to double-check your costume before walking out to a children's party. Then again maybe this dude did but he couldn't see that he was wearing the bodysuit backwards through that giant dome piece.
He ends up walking out in front of a crowd of children with the tail on backwards. Meaning it no longer functions as a tail. There seems to be some genie-looking woman running the show too and she tries to block out what these kids are being exposed to but it doesn't work out too well.