There is a monster upstairs

Gavin is seeing monsters in his closet. He wakes up early every morning, crying. He runs to our bedroom and says, "there is a monster upstairs, in my closet." I thought maybe i could try to turn it into a "good" monster. He has seen Monsters the movie and so i told him it was Sully. I told him Sully wasn't trying to scare him, but that he wanted to tell him a joke. Gavin had me go to his room to tell Sully to leave. I told Gavin that Sully said he was sorry and that he didn't mean to scare him. I told him that if Sully shows up again just tell him to leave. So now Gavin tells me that he told Sully to leave, but he is still scared. Today Gavin was having a pretend conversation with Sully. He was saying this... "You be nice to me Sully".."Okay".." Don't say okay to me, okay Sully?...." oh okay".... It was really funny. I can't remember the whole conversation.