Kate recognizes that Cartwright is talking about fear toxin when he mentions dosing Mouse with a "concoction" developed by Jonathan Crane; she encountered it during Elseworlds, Part 2 (2018).
This is the first episode of the series to not feature Meagan Tandy (Sophie Moore) besides the crossover episode Crisis on Infinite Earths: Part Two (2019).
The flashback featuring Kate and Beth at the aftermath of their Bat Mitzvah was to have been included in Pilot (2019) but was cut for time.
There are several characters nicknamed Mad Dog in DC Comics, but the most widely known is Martin Hawkins, an Arkham Asylum patient.
The episode title is a reference to the Queen of Hearts' quote "Off with her head" from 'Alice in Wonderland'.