Joker is seen with a sidekick who is a little person wearing an orange & black outfit and a Punchinello nose. This is Gaggy, a mostly forgotten minion of the Joker who made his first appearance in Batman #186 which was released in November 1966. During a fight, Gaggy jumps on the shoulders of one of the Batmen and covers his eyes. This image is also on the cover of the comic where he made his first appearance.
When Marvel-Batman knocks out a criminal, he explains it by saying "Been working out" and pumps his arms. This is the same action and excuse used by Clark Kent in Superman II (1980).
First view of Catwoman in a new outfit and her last appearance with dialogue.
Multiple variations of the Batman can be seen after them coming through the wormhole, including Batmen from Batman: The Dark Knight Returns, Part 1 (2012), Batman: The Animated Series (1992), Batman Beyond (1999), and The Batman (2004).