Goof (revealing mistake): Animation error: When Rocko is wearing his normal shirt, he is wearing nothing below his waist. He clearly has no pants/underpants of any sort on. But whenever his shirt is removed, he GAINS a pair of underpants.
Goof (continuity error): When Mr. Dupette appears for the first time, he is Rocko's boss as Super-Lot-O-Comics. In all subsequent episodes he works for Conglom-o.
Goof (continuity error): In the earliest scenes, Rocko's old vacuum is called the "Suck-O-Lux." In the last scenes that have the old vacuum, it is called the "Suck-O-Vac."
Goof (continuity error): When the whole Wolfe family is sitting at the dinner table. The camera shows all of the Wolfe family eating the Moose on the table but when the camera changes angle the Moose is uneaten.
Goof (continuity error): When Heffer is told that he is adopted he asks about a birthmark (which is a butcher's outline for cutting beef) but in any other segment of the show when Heffer's birthmark aria is shown there is no birthmark.
Goof (errors made by characters, possibly deliberate errors by the filmmakers): At the end of "Kiss Me, I'm Foreign", Rocko remarks "I'm a citizen!" after he receives his INS papers and a Green Card. A Green Card is issued to non-citizen residents of the United States.
Goof (continuity error): In the fortune cookie factory the typeset writes Bad luck and extreme misfortune will infest your pathetic soul for all eternity, but when Filbert opens the cookie the word extreme is missing from the fortune.
Goof (continuity error): The Hippo Lady's voice changes from episode to episode. In some episodes she talks like Ed Bighead, in other episodes, she has a raspy, more feminine voice. (Actually she has both voices. Her normal voice is effeminate, but when she gets aggrieved - usually by Rocko inadvertently) she takes on her more manly voice and utters her catchphrase, "How dare you!"
Goof (continuity error): In "Put to Pasture", when Rocko is remembering when he and Heff first met he says that they met in high school. But in the Season 1 segment "To Heck and Back", Rocko and Heff were remembering a story about when they were in the 3rd grade together.