Fungus is shown to be very clumsy and cowardly, the latter proved when Randall furiously threatens him to put him through the shredder if he does not bring another door to the station. He is generally incompetent and always bullied and abused by Randall, never having the guts to stand up to him.
Initially, Fungus is a kind person and means well, even apologizing to Mike about his capture. He eventually falls victim to the machine himself. After Randall is banished to the human world and Mr. Waternoose is arrested by the CDA, Fungus is a lot happier and takes on the job of making children laugh.
Fungus is a small red monster with legs similar to those of a chicken and three eyes.
In the film, Fungus is Randall's scare assistant. He is rather cowardly and wimpy due to the wrathful temper of Randall and helps him with his plan to revolutionize the scaring industry, although he regrets it.
He helps Randall (out of fear) to create the Scream Extractor. Fungus is initially a kind person and means well, even apologizing to Mike about his capture. Due to Sulley's timely intervention, Fungus falls victim to the machine himself, which blanches him white, proving that it would cause great physical harm if used on a human child.
Fungus is later seen operating machine's controls once again, this time testing it on Boo as Randall and Mr. Waternoose watch on in anticipation. He also assists Randall as they pursue Sulley and Mike (who had rescued the girl from the device) but falls behind due to a crowd of monsters congratulating Randall for supposedly breaking Sulley's Scare record, courtesy of Celia at the PA system's controls.
After Randall is banished to the human world, Fungus is a lot happier and takes on the job of making children laugh. He is also grateful to his new boss Sulley, both for forgiving him for conspiring with Randall and assigning him a job on the newly-commissioned Laugh Floor. It is unknown if he also became a scarer, as it was revealed in Monsters, Inc. Scream Team Training that the monsters still use screams.