Screwball is a clown who lives in Joseph's house. He makes snake balloons and sells "candy" which is meth. He appears to love children in a weird way. He attends Bowser Junior's sixth birthday party, along with Joseph, and makes snake balloons for Bowser Junior and his friends.
In Bowser Junior's Halloween, Screwball is seen in a box. He doesn't have any candy but instead gives rocks to Junior, Joseph, and Toad because he recently had a rock party. Cody receives a candy wrapper as Screwball did not have enough rocks. He offers Junior and his friends to go in his box. When Junior and his friends leave, Screwball announces that he loves them.
Likes and Dislikes
Being a clown
Getting his way
Making snake balloons
Hershey's Candy Bar
Not getting his way
Going to jail
Some characters do not believe Screwball exists due to his name (such as Bowser's Mom and Black Yoshi, albeit they never met him)
In Bowser Junior's Halloween, it appears that Screwball does not know Junior and his friends and that Junior and his friends do not know him, despite having met each other in earlier videos.
Screwball is named after a clown who visited Logan's birthday party when he was young.
Screwball was actually originally intended to kidnap the kids in Bowser Junior's 1st Grade! Part 5, which would've caused the school to shut down and everyone pass by default, but Logan decided not to go down that route.
Screwball believes that meth is candy.
Screwball has gone on dates with Joseph's mom multiple times, despite the fact that she's dead.