The short starts with SpongeBob and Mr. Krabs at the Krusty Krab, which is decorated for Halloween. Mr. Krabs gives SpongeBob a garbage bag filled with moldy kitchen sponges and tells him to take the bag out to the dumpster. On the way out, SpongeBob trips on a bucket and all of the moldy sponges start flying.
As SpongeBob is going to get out of the sponges, he sees the green moldy full moon. Because he is on the moldy sponges, he himself turns into a Moldy Sponge for the rest of the short, which makes him green and grow big eyebrows and mushrooms. Seeing that he turned evil, he laughs until he sees Mr. Krabs coming out of the Krusty Krab.
Mr. Krabs complains that he told SpongeBob to throw away the moldy sponges and that he has to do it himself. He takes SpongeBob and carries him into the dumpster, thinking that he is a moldy sponge. He groans about Mr. Krabs throwing him out as the short ends.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ Danger HQ - Norman Dane [SpongeBob sees the full moon.]
‣ Dramatic Bridge 4 - Phil Green [SpongeBob turns green.]
‣ Pirate's Opus - Michael Bolger, Nicolas Carr [Mr. Krabs puts SpongeBob in the dumpster.]
- This short is available on The Pilot a Mini-Movie and the Square Shorts DVD.
- The way SpongeBob transforms is similar to that of a werewolf.
- When SpongeBob transforms, his shoes, socks, pants, and Krusty Krab employee hat turn green as well.
- Moldy Sponge looks similar to the Abrasive SpongeBob from the episode "The Abrasive Side."
- This short marks the second time SpongeBob transforms into another animal rather than a shape. The first time is in "I Was a Teenage Gary."
- On the Pilot a Mini-Movie and the Square Shorts DVD, this short is titled "The Creature Frumunda the Sink."
- If the kitchen sponges were alive at one point, that would technically make SpongeBob a zombie, since the mold acts as a zombie virus.