In its first appearance in "Quackor the Fowl", Mandark performs the same experiments that Dexter performs on Monkey but finds nothing unusual about it and decides to bring it to show and tell, later that night Ducky overhears Mandark's desire to destroy Dexter's laboratory so Ducky becomes Quackor and begins to destroy the lab.
The racket wakes up Monkey and he becomes his alter ego and tries to communicate with Quackor, but it leads to fighting. After a while it is revealed that they are evenly matched, and the fight lasts all night upon seeing the sunrise. Quackor turns back into Ducky and flies back into Mandark's house.
Dexter and Mandark try to show off their pets' tricks in class, but they are too tired from fighting to do anything. Quackor returns in A Quackor Cartoon the beginning is quite similar to the previous episode and they fight until Monkey punches Quackor so hard it lays an egg revealing Quackor to be female upon realizing this Monkey falls in love with her and they go on a date at the end.
- Like Monkey, Quackor's vocal effects are provided by Frank Welker.
Grim Adventures of Billy & Mandy