Jonny Frost was first seen holding down Harleen Quinzel while the Joker electrocuted her. After this, he accompanied the Joker and Harley Quinn to a strip club for a meeting with arms dealer, Monster T.
He later informed the Joker of Harley's whereabouts in Belle Reve prison. He was present while the Joker captured Captain Griggs and attacked Van Criss' facility to find out how to disable Harley's nanobomb.
- Before his role was revealed, Parrack was rumoured to be playing Slade Wilson aka Deathstroke.
- Jonny Frost is a main character in the 2008 comic Joker. He serves as the narrator throughout the comic, which ends in his death.