Mr. Sludge was originally shown to be in an obese slug-like appearance with moss, olive green skin and yellow eyeballs and wore a navy blue jacket, a lavender and blue striped tie and a white long sleeved shirt. However in his true form, he is slender, muscular and skinny, has fair skin and brown hair and a very handsome smile.
Role in the episode
Mr. Sludge originally had a factory in Spoonerville called Slime Co. and was aided by his assistant Melvin, whose name Sludge always got wrong despite Melvin working for him for 12 years. However, the smoke from the chimneys of the dangerous factory polluted the air, which affected the plants in Goofy's garden. Goofy was convinced by his son Max to go to Slime Co. and make him stop polluting, but this time he did not work as Sludge sent Goofy on his way. Goofy, with some encouraging from Max decided to run for Mayor in order to get rid of Slime Co. once and for all.
However, Sludge was able to bribe Goofy's opponent and neighbor Pete to be on his side. After a while, Sludge saw that Pete was no good and so decided to deal with Goofy himself by putting tanks of toxic waste in Goofy's garage to frame him. But Goofy opened the garage door and the toxic waste got into contact with sunlight which caused it to mutate into a creature. Goofy went to Slime Co. to confront Sludge about what he did and just then, the creature arrives and picks up Goofy. But the creature disintegrates when it comes into contact with the clean air from a jar Goofy had.
Sludge sniffs the clean air and thinks that he is melting but the air only melts the green parts off him, revealing his true appearance. Sludge decides to knock down Slime Co. and builds a ballet school there instead.