The episode begins with the unveiling of a fully-restored Ultrasaurus skeleton. Not only has a complete Ultrasaurus skeleton never been discovered, it was shown in 1996 (a year before this series began) that Ultrasaurus was not a valid genus of dinosaur, the bones originally named "Ultrasaurus" actually being from two previously-known genera.
Just before Batman and Batgirl happen upon Mr. Freeze's empty suit, faint, animated impressions can been seen in a few frames including people and dogs.