The new baby getting saddled with a special name is initially going to be named Juppiter, with 2 Ps; the parents may not know it but in ancient Rome it was originally spelled that way (Iuppiter or Juppiter) before Jupiter became the standard. Additionally, never is it made clear what sex the baby is, but in theory Juppiter should be a boy's name, and the last-minute change to Callisto, explained by someone else's using the name first, could also be due in part to Callisto's being a girl's name.