Nailbunny was Johnny's first and last pet, a rabbit whom he fed once and then nailed to a wall. Only the preserved head (which was torn from the body by Mr. Eff) remains by the end of the comic, the rest of the body apparently unnecessary for the afterlife. It is unclear whether the disembodied head of Nailbunny was actually given the ability to levitate by the supernatural force that permeates Nny's house, or that Johnny is simply hallucinating during his interactions with the dead rabbit.
Among the group of Johnny's "voices," Nailbunny appears to represent Nny's conscience and "voice of reason," a role he on occasion expresses exasperation with. He is responsible for persuading Johnny not to kill himself, and also acts as a conversation partner during some of Nny's more introspective moments regarding his life and killing sprees. After Johnny dies and is subsequently returned to the newly-rebooted universe, Nailbunny no longer appears, although on at least one occasion it is suggested that Nny still hears his voice.