When first shown at the very beginning of the film, Thaddeus struggles with his test simulations, leaving a door open and utterly messing up on his attempt to frighten the mechanical child. He tripped over things such as a soccer ball and a skateboard before landing painfully on a pile of jacks on his backside. He is accident-prone and a bit of a coward.
At the end of the film, he is seen returning to the Laugh Floor from a child's room, and he seems to have successfully made that child laugh.
He also appears in Mike Wazowski's company play "Put That Thing Back Where It Came From or So Help Me", portraying the Sushi Chef during the restaurant scene, as well as singing with the rest of the cast at the play's finale.
- In the CD Read Along version, if it's played on the computer, there is a very very rare snapshot in which Bile was originally going to roar at the robot child. This was likely an early work-in-progress footage, because in the final version, Bile simply bared his claws before the robot screamed.