Character mistake: Poison Ivy tells her beloved plant "I won't clip off any more of your beautiful petals." She clips off the whole flower, not really "petals." (00:14:35)
Character mistake: The French spoken by the waiter of the cafe is phony in a pretty atrocious way for a supposed high class restaurant. Can't even pronounce "monsieur" right, it's merely a tacked-on accent. (00:04:10)
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)
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)
Christmas With the Joker - S1-E38
Other mistake: Robin is trying to change channel but is unsuccessful, because the Joker hijacked all transmissions. Perhaps also because the remote control he has in hand has just one button. (00:04:40)
Character mistake: When Batman uses his magic computer to analyze Langstrom/Man-Bat, lots of lovely gibberish appears on screen, with some notable typos such as "Bat membaaanes", "Sedum Chloride D", "Mammac higi Index Gat harmal nomeaace at padiotion." Your guess is as good as mine for the last one. (00:21:10)
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.
Other mistake: Batman sees the robbery happen, but he has yet to start his chase when the rotund old lady is deep into discussion with the policeman. (00:03:00)
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)
Other mistake: Gordon has some impressive ceiling fan in his office, since not only one of its blade supports a full-grown adult hanging by the back of the neck to it, but it even keeps working as usual during it. (00:21:30)
Other mistake: The Scarecrow and his goons escape on an airship, which has the control bridge in the gondola under the main structure. Batman reaches the top of the airship, and so does Anthony the goon...but he does it from a trapdoor on the roof of the gondola. There's a whole structure in between he skipped. (00:15:10)
Factual error: It doesn't seem likely Maxie Zeus could've survived being both electrocuted and hitting concrete real hard at least without some serious injuries.
Character mistake: The news program Stromwell is watching at the beginning of the episode displays a picture of Commissioner Gordon with the caption "Comisioner." (00:02:00)
