Have You Seen This Snail? - S4-E3
Continuity mistake: Have You Seen This Snail: After the customer asks for a refund it cuts to SpongeBob crying in the kitchen, and when Krabs walks in the door opens at the left side with no knob, but when Krabs tells SpongeBob that a problem can be solved with a little hard work, that door now opens at the right side with a door knob.