I've Got Batman in My Basement - S1-E20
Revealing mistake: Sherman puts down the Jr. Detective box to try to get back the stuff the bullies grabbed. He sets the box on one of the steps, but the way it is drawn defies gravity. (00:03:40)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Batman looks at the vulture after outwrestling it, and then, sprints to get his 'rang back. When he looks out he's got a cut on the suit, on the left, but when he fetches the weapon the torn part is gone. Cut away, and now the tear is back and doubled over to the other side. (00:02:55)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Sherman hangs the two front pages overlapping in close-up, at distance in the next shot. (00:21:15)
I've Got Batman in My Basement - S1-E20
Continuity mistake: When Mrs. Grant gets in the basement at the end, the Penguin is crushed under a long plank, different from the shelf that dropped on him earlier. (00:20:40)
I've Got Batman in My Basement - S1-E20
Revealing mistake: Penguin grabs the umbrella from the floor. For a moment you can see two umbrellas, and in the next shot the top with the smashed rotating blades is fixed. (00:19:50)
I've Got Batman in My Basement - S1-E20
Continuity mistake: When the Penguin melts the front door lock, the holes on the door change distance between shots. (00:16:35)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Mrs. Grant casts a shadow on the stairs that reaches a different point in different shots even if she did not move. (00:12:35)
I've Got Batman in My Basement - S1-E20
Continuity mistake: Batman and the kids approach the exit; you can see Roberta touching the push handle, but in the next, closer, shot they have yet to get there and Batman kicks the door open (without trying the panic bar). (00:07:25)
I've Got Batman in My Basement - S1-E20
Continuity mistake: From below, Sherman's red hair is visible, so he is on the left side of the sack of seed. In close-up though, he's in the middle, by the hole it leaks seed from. (00:05:15)
I've Got Batman in My Basement - S1-E20
Revealing mistake: The thief kicks away the canister bird seed was falling on...and the bird seed keeps landing in the same spot, which at this point is thin air. (00:05:10)
I've Got Batman in My Basement - S1-E20
Revealing mistake: The two kids grab a couple of items from Sherman's detective box, but the items never go away, a duplicate is spawned instead. (00:03:30)
I've Got Batman in My Basement - S1-E20
Continuity mistake: The talon cuts on Batman's cape change in space and position between shots; they are firmly on top of the shoulders at the end of the struggle, but they were lower during the actual fight. (00:02:20)
I've Got Batman in My Basement - S1-E20
Continuity mistake: The size of the egg the Penguin's guys steal changes throughout the opening. It's twice as big as the ginger's hands when he holds it, but passed through a small triangular (for some reason) section they cut in the window, and when Batman reveals himself the egg is smaller.
I've Got Batman in My Basement - S1-E20
Continuity mistake: The balls of the bolas that tie Penguin up change position between shots. (00:18:00)
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
Character mistake: One of the books Sherman is getting his detective stuff from is called "Crime and It's Causes." It must not be a very good book. (00:11:15)
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: Because he stole a chemical from his lab.
But Batman knew that with it, Clayface could permanently retain his shape and Clayface desperately wanted to be Matt Hagen again. In a sense, Batman stopped Clayface from becoming human.