Be A Clown - S1-E11
Continuity mistake: Batman sees the Joker and the kid on the roller coaster platform, but he's animated going in a different direction instead of just hopping over the rails. (00:18:35)
Be A Clown - S1-E11
Continuity mistake: When Batman jumps on the tracks to start chasing Joker, the lever that starts the attraction is on the wrong platform. (00:18:45)
Be A Clown - S1-E11
Continuity mistake: The Joker pounces Batman when he gets on his cart. When they are fighting in the background and Jordan reacts to the sight of the tracks ahead, the cart is much longer than it should be. (00:19:45)
Be A Clown - S1-E11
Other mistake: When Jordan comes out of the truck, something went wrong with perspective and/or proportions, because with his leg bent he is practically as tall as the truck door, and he's a child.
Be A Clown - S1-E11
Character mistake: The magician's name on the poster is "Proscuitto", which is a wrong spelling for Prosciutto (ham). The misspelling is inconsistent throughout the episode; it is wrong the first time Joker shows the poster, then it's fixed at the fun fair and on tv. The font used is also different.
Plot hole: The two agents split; the rookie goes down an alley, chasing the two henchmen, who reached their car and chase him back down the alley almost running him down. Batman saves him though, destroys the car and quickly interrogates a suspect. Somehow though he also manages to save Montoya, who went inside the warehouse right away as they split the warehouse. The timing does not work.
Continuity mistake: The Clock King slashes Batman's chest logo with his clock hand cane leaving it sliced up. A few shots later it's intact.
Other mistake: At the beginning of the episode, the truck of the "Gotham Globe" delivers to the newsstand a nice bunch of copies of the newspaper, which naturally bears the name..."Gotham News" (00:01:20)
Continuity mistake: The boat with the gas-emitting garbage goes past the bridge, and its odor approaches the bridge trailing behind, from the left of the screen. A few seconds later it also intoxicates the street workers, but the miasma approaches from the right. (00:02:00)
Revealing mistake: When Alfred proudly shows the sketch with his joke, the top part of the shower pipe disappears in some frames. (00:03:15)
Character mistake: Batman's computer warns him about the "air born gas emanating from river front district." It's airborne, and riverfront. (00:07:10)
Other mistake: Batman's lungs have plot armor; he has all the time to put his mask on even after exposure to the gas, and he reacts to it coughing at first. Nobody else in the episode reacts with a cough. (00:07:55)
Continuity mistake: When Captain Clown lifts the drum to toss it into the river, the lid shows no holes; Joker punches a few in it earlier. (00:11:55)
Continuity mistake: Captain Clown chases Batman with its arms outstretched, except in the long shot with the crane; he is walking with his arms down his sides. (00:15:45)
Continuity mistake: Captain Clown gets pressed into a block of scrap metal. The ascot faces the front side (the one facing the direction the conveyor belt carries it to) in the first shot, then Joker dumps more junk on Batman and goes away sitting on the block; the ascot is facing now the back. (00:17:15)
Answer: She escaped off-screen and created a copy of herself to fool everyone.