SpongeBob Meets the Strangler / Pranks a Lot - S3-E20
Continuity mistake: When The Strangler and Spongebob arrive at the pineapple, look at the door: there is no doormat below it, but a couple minutes later Spongebob pulls a key out from under the doormat that was not there before.
SpongeBob Meets the Strangler / Pranks a Lot - S3-E20
Continuity mistake: In "Pranks-A-Lot" when Sandy flies out of her dome in an escape pod to Texas, she leaves a big hole on top of her dome. In the next shot, it's gone. Very noticeable mistake.
SpongeBob Meets the Strangler / Pranks a Lot - S3-E20
Continuity mistake: In "Pranks A Lot": SpongeBob and Patrick are going to burn Mr. Krab's dollar, so he throws water on them and they become visible. Patrick is holding Mr. Krab's dollar. When he says "We're visible again", and he and SpongeBob start to scream, the dollar completely disappears.
SpongeBob Meets the Strangler / Pranks a Lot - S3-E20
Continuity mistake: In Spongebob Meets The Strangler, the Tattletale Strangler's dots on his head change numbers constantly. Sometimes there are 5 on his right, sometimes 6, sometimes his left side has a scar and 5 dots, sometimes a scar and no dots.
Answer: I believe this is the Season 6 episode "Spongicus".