When Batman mentions meeting the Scooby Gang at the malt shop on the corner of Spears and Ruby, it is a nod to Joe Ruby and Ken Spears: the two men who developed the original Scooby Doo cartoon idea.
Jeffrey Combs reprises his role as The Question from Justice League Unlimited (2004)
Poison Ivy has a flower named Georgia. This is most likely a reference to Georgia O'Keeffe, who is famous for painting flowers.
This is the thirteenth entry in the direct-to-video series of Scooby Doo films.