Jim Rash, the voice of the Riddler, appeared in an episode of "Community" where his Batman-actor-themed code name was "Voice of Diedrich Bader," the actor who reprises that very role for this episode.
There was widespread supposition that Margot Robbie would provide the voice of the title character, seeing as she has played her several times in live action films. Robbie however was too busy filming Birds of Prey (2020) to get involved so casting took place with Kaley Cuoco landing the voice role.
A wall falls on Harley, but she remains uninjured because she goes through a hole caused by the explosion. This is probably in reference to Steamboat Bill, Jr. (1928).
After Ivy--voiced by Lake Bell--"saves" Harley--voiced by Kaley Cuoco--from the acid, Harley tells her that she wants to "crawl back into that acid and die." Cuoco's character Penny in The Tangerine Factor (2008) said a similar line ("crawl into a hole and die") after learning that her boyfriend Mike posted a blog about their sex life.