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)
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.