A Flea in Her Dome / The Donut of Shame / The Krusty Plate - S5-E11
Continuity mistake: In "A Flea in Her Dome", Patrick asks Spongebob to get on Sandy's shoulders. Then, he climbs onto Spongebob's shoulders. In the next shot, they are suddenly next to Sandy's tree.
A Flea in Her Dome / The Donut of Shame / The Krusty Plate - S5-E11
Continuity mistake: In "A Flea in Her Dome", Patrick gets bitten by a flea and his chest is covered in bites. He takes out a pencil and connects some of the dots to make a horse. A few shots later, the horse and the bites disappear.
A Flea in Her Dome / The Donut of Shame / The Krusty Plate - S5-E11
Factual error: In 'A Flea in Her Dome' Sandy opened up the door for water to fill her dome. The water even replaced the air on the inside which was above the door, which isn't possible because the air would have to go down through the door to escape the dome.
A Flea in Her Dome / The Donut of Shame / The Krusty Plate - S5-E11
Continuity mistake: In "The Krusty Plate", Spongebob finds that one plate has a brown smudge on it. After an attempt to clean the plate, he lifts it up and the smudge is now a light shade of green.
Answer: I believe this is the Season 6 episode "Spongicus".