I've Got Batman in My Basement - S1-E20
Other mistake: Toss a brick into a pile of empty boxes, and they won't fly around like it is shown. The heavy brick will sink into whatever hits and possibly other boxes will be affected; here the brick does not deform the box it hits and every single cardboard acts like bouncy balls. (00:13:30)
I've Got Batman in My Basement - S1-E20
Other mistake: The Batmobile moves because Roberta is pushing the gas pedal...but one of the first shots when we see the car move, shows Roberta rolling to the back of the cockpit because of the acceleration. The car does not slow down or anything, though. (00:09:35)
I've Got Batman in My Basement - S1-E20
Other mistake: Penguin and the goons take an impossibly long time to get to Batman once he's incapacitated by the gas and is semi-unconscious at the railing. (00:07:40)
I've Got Batman in My Basement - S1-E20
Other mistake: Sherman touches by mistake the "OFF" button...which turns the conveyor belt on (there is a separate ON button...for some reason). Not just that; the buttons also look completely different between shots; first they are circular buttons with colored lights on top, then they are nondescript small levers. (00:06:55)
I've Got Batman in My Basement - S1-E20
Other mistake: The kids manage to drive away with the Batmobile simply operating the gas pedal, but they show that the gear is manual and it has three pedals.
Answer: She escaped off-screen and created a copy of herself to fool everyone.