Batman The Animated Series Easter Egg - Bacta Tanks and Freezie Feet

Mark Hamil, the voice of the Joker, also did the voice for Mr Freeze's former boss who appeared in this episode.
In the episode, Batman revives a freeze victim, he uses a total submersion chemical tank, similar to the one Luke Skywalker(Hamil) was healed with in Star Wars: The Empire Strikes back.
Later in the episode, Batman is hung upside-down by his feet in Mr Freeze's ice cave, another situation that Luke found himself in during Star Wars:The Empire Strikes back.
This wouldn't count as an easter egg, except not many people know Hamil voiced a character in that episode.