Porkbelly

Porkbelly is the "world's most sinister psychokinetic angelfish." He only appears in Captain Underpants and the Sensational Saga of Sir Stinks-A-Lot. He is the assumed predecessor of Flippy, except Porkbelly isn't a cyborg.

He’s is voice by Len Forgione in the Sound-O-Rama Audiobooks.

History
Porkbelly appears in the Dog Man: The Bark Knight Cometh comic; he does not appear in any Dog Man books though.

Powers
It seems as though Porkbelly has the same powers as Flippy: telekenisis. In Captain Underpants and the Sensational Saga of Sir Stinks-A-Lot, Porkbelly was disguised as Mecha-Petey, so it can be inferred that Porkbelly was using his telekentic mind powers to control the fake Mecha-Petey.

Trivia

 * Porkbelly has the same name as Professor Poopypants' assistant in Captain Underpants and the Perilous Plot of Professor Poopypants.
 * Porkbelly was probably the inspiration for Flippy, or a beta form.