The Hoppin' Jack is a Hardmode pumpkin-like enemy that will only appear at night during the Halloweenseasonal event, or in Graveyards any time of year. He attacks by hopping towards the player in a manner identical to most Slimes. The difference, however, is that the lower on health he is, the quicker he becomes.
Notably, despite using the Slime AI, he is not treated as a slime for most other purposes. Hoppin' Jack drops no Gel on death, will remain hostile to a player with Royal Gel equipped, and killing one is not necessary to earn the Gelatin World Tour () or Slimer/King of Slimes () achievements.
The name Hoppin' Jack is a reference to Spring-heeled Jack, a creature from British folklore.
The Bestiary entry for the Hoppin' Jack: "This particular pumpkin seeks revenge for being carved. His hearty leaps become quicker the more he is carved into."