Jeremiah lists off possible aliases starting with "J", including Jack, John and Joseph (all of which are aliases the Joker has gone by in the comics).
This episode was planned out five years in advance, when Season 1 was on the air. According to John Stephens, "When I came on the show in season one, [creator] Bruno [Heller] pitched me what he saw the ending as and it's very close to that, his initial idea".
Camren Bicondova stated, "I firmly believe that part of leaving a legacy and being a part of a legacy means knowing when to pass the torch to someone else."
Jeremiah Valeska makes a reappearance under a new moniker and identity, having last appeared in the episode "Ace Chemicals". Cameron Monaghan has described the character's appearance as "vicious, nightmare-fuel horror." After falling in the chemical vat, he has undergone an evolution figuratively becoming "an amalgam of Jeremiah and Jerome" who, according to showrunner John Stephens, leads to Batman's arch-nemesis "The Joker" somewhere down the road.
It was ultimately Camren Bicondova herself whose decision it was to be recast in the series finale, feeling that was best for the character. She felt that an older actress should play Selina's adult self and referred to Simmons as the "perfect" successor. Bicondova shared her notes on the character with Simmons, and the two spent hours discussing Selina's unseen character development in the ten years between "They Did What?" and "The Beginning.