Continuity mistake: When Homer bangs on the screen in the testing booth, the little sign on the top left of the glass that was there earlier is no longer there.
Continuity mistake: The house is ripped from its foundations, but later on when it falls down the waterfall you can see the floor is completely intact.
Continuity mistake: After the Simpsons are selected for the 1895 reality show, they're shown the video confessional room, with the only tech in the house. When Marge is in this room confessing about her blue hair, the doorknob is on the right, but when Bart is inside confessing that he's miserable, the doorknob is on the left side of the door.
Continuity mistake: When Homer brings his family to Lenny's apartment, as Lenny shuts his front door, its doorknob is on the right, but when Homer and his family depart Lenny's crazy apartment, now that front door opens the opposite way, with its doorknob on the left.
