When first shown at the very beginning of the film, Bile struggled with his test simulations, leaving a door open and utterly screwing 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 was accident-prone and a bit of a coward.
Right before Sulley's scare demo, Bile screwed up on yet another attempt to frighten the mechanical boy, instead of lulling him to sleep, much to Mr. Waternoose's frustration. Bile claims he was going for a "snake/ninja approach, with a little hissing."
He is later scene near the entrance to the factory amongst the other monsters watching Mr. Waternoose get arrested by the CDA.
At the end of the film, he was shown returning to Laugh Floor F from a child's room after successfully making that child laugh, presumably by performing the accident he got in the simulation at the beginning of the movie as he was seen with jacks on his bottom.
In the Playstation 2 game of Monsters Inc. At the start of level 1, Sulley is introduced to Thaddeus Bile by Mr. Waternoose, Thaddeus Bile wants to show off his scare but realizes he forgot his manual and left it at Mr. Waternoose's office. Sulley decides to sneak around the factory and gets the manual but then Thaddeus realizes he forgot his key card, Sulley decides to sneak into Mr. Waternoose's office and successfully retrieves Thaddeus key card, but then it is time for him to go home.
Bile tries to be a scary monster...
...but the mere sight of the mechanical child freaks him out.
Bile among the monsters witnessing Waternoose's arrest.
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 early work-in-progress footage because in the final version, Bile simply bared his claws before the robot screamed.
In the Playstation 2 game Monsters, Inc. (video game), Thaddeus Bile makes a cameo on Level 1 and sends Sulley on a fetch quest to retrieve his manual then his key card.
His name, "Phlegm" Bile, are two different fluids that form in the throat and digestive tract. Bile is a bitter fluid that helps with digestion and Phlegm is thick substance that is composed mucus.