Surf's Up! Joker's Under! - S3-E10
Other mistake: An amazingly precognizant Dick Grayson is already wearing his surfing togs before Commissioner Gordon calls to say that Joker has invaded the surfing community. (00:04:30)
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Suggested correction: Dick isn't amazingly precognizant. He's wearing swim trunks while using the rag to prep his own surfboard. Barbara Gordon was already at the beach with Skip, and Dick is heading to the beach with his surfboard as well (00:04:34).