In the comics, Pamela Isley, also known as Poison Ivy, is an eco-terrorist with the power to control all plant life and enemy of Batman, she is married to Harley Quinn.
Poison Ivy poster
The comic Shazam! Fury of the Gods Special: Shazamily Matters includes various in-universe marketing ephemera relating to characters including Poison Ivy. However, it was never addressed if these characters do exist in-universe or are just fictional characters created by the marketing in-universe.
