Continuity mistake: After going through the curvy air ducts, Mr. Krabs, Spongebob, Squidward and Patrick land in a metal box. In the next shot, Mr. Krabs picks up a Krabby Patty wrapper that wasn't previously there.
Continuity mistake: Patrick smashes a walkie-talkie that Squidward is holding. In a few shots, the smashed pieces that were on the ground have disappeared.
Continuity mistake: Patchy the Pirate wakes up surrounded by other people in the green room. Lincoln lifts up his hat to reveal a Spongebob plush, and Patchy points at it while lying on the floor. In the next shot, his arm is now at his side.
Answer: I believe this is the Season 6 episode "Spongicus".