As Batman drives the Batmobile alone to Gotham Police Headquarters after the opening credits, the shot after the Batmobile exits the Batcave includes Robin in the car. It is a re-used shot.
Susie and the cheerleaders are practicing a cheer for a basketball game, but their cheer ends with the line, "Let's make a six!" There is nothing in basketball that would make this line make sense; the most points a team can score on any one possession is four (a three-point basket followed by a free throw, if the shooting player is fouled in the act of shooting but makes the three-pointer anyway). However, if you look at the wider shot of the court, you can see a banner proclaiming that the team are the champions 5 times in a row, so they are almost certainly referring to a 6th consecutive championship.