When Batman opens the garage while mentioning he needs to retool one of his prototypes, the first BatMobile we see pays homepage to the BatMobile from the 1989 movie "Batman" with the fins and the jet exhaust.
Whenever the new batmobile is ready Alfred says do come in one piece, a possible reference to the movie Batman and Robin.
The first appearance of gearhead.
Will Friedle, who voices Gearhead, previously voiced Batman-- albeit a future Batman-- in Batman Beyond (1999).
When Batgirl first gets into the new Batmobile she asks "Ooh, Corinthian leather?" Corinthian leather is not an actual type of leather at all, it is a marketing term introduced it in 1974 by Chrysler to describe premium leather seat material. Celebrity Ricardo Montalban helped popularize the term in car ads.