The Good, the Bad, and the Wallaby / Trash-O-Madness - S1-E6
Continuity mistake: Rocko is cleaning the fridge and he smells rotten sausage links so he throws them out in the trash can. The next shot of the trash can, the sausage links magically disappear.
A Sucker For the Suck-O-Matic / Canned - S1-E8
Continuity mistake: In "Sucker for the Suck-o-matic," the TV opens up Rocko and Heffer's heads to scrub a weird product on their heads to make them buy the Suck-o-matic. The TV leaves their heads open when taking their brains out to dribble. In the next shot the heads are closed while the TV dribbles the brains. Then in the next shot, their heads are back open while the TV puts them back.
The Good, the Bad, and the Wallaby / Trash-O-Madness - S1-E6
Continuity mistake: In "Trash-O-Madness," Rocko gets beaten up by the Trash dog. When Rocko goes back in his house, facing the screen his tail is fine, but in the next shot there is a huge bite mark in it. Then when he is in the kitchen, in the next shot, the bite mark disappears.
Carnival Knowledge / Sand In Your Navel - S1-E9
Continuity mistake: The sign that the slug is hammering into the ground near the big roller coaster changes fonts three times.
Leap Frogs / Bedfellows - S1-E2
Continuity mistake: In "Bedfellows", when Heffer goes to bed he is only wearing his underwear. However, in one close-up shot during the sequence where Rocko tries to stop his loud snoring, specifically the portion where he uses a cattle prod, one of the purple straps of Heffer's overalls is over his shoulder.