Dib Membrane is an eccentric young boy(12 yrs old confirmed in the show) who is obsessed with the paranormal. He is the brother of Gaz and the son of Professor Membrane, as well as Zim's greatest nemesis. He attends school with Zim, and is determined to stop him from conquering Earth and expose him as an alien, though almost nobody believes him. He is highly unpopular at school and at home for said obsession with the paranormal, and is often dismissed as "crazy" or "insane."

In Issue #0 of the Invader Zim comic "TruthShrieker", it is confirmed that Dib's (and Gaz's) last name is "Membrane". He is the author of an article about Zim's mysterious dissapearance and the article is by "Dib Membrane".