Revealing mistake: When the Penguin is sliding down the zip line, just before he hits Batman you can see Batman throwing a punch at nobody, he is swinging at empty air.
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Trivia: Cesar Romero refused to shave his moustache for the role of Joker, so it's still visible under his makeup.
Answer: The Riddler doesn't sing at all. He yells to the henchmen on board, "Prepare to repell boarders!" He does it in a almost musical way, true, but there's no song.
CCARNI ★