in the episode "Mrs. Puff, you're Fired" when the new instructor comes in, he smashes the door cleanly from the doorframe. Then when he throws one fish out for "talking", he throws the fish through a door next to the door he just smashed through. then, when the instructor throws another fish out for eating in class, he throws the fish through the SAME DOOR he threw the other fish out, except it's magically fixed. Also, the first door that the instructor smashed through, is back in the doorway, except it has a hole in it. Bikini Bottom has some strange doors.