Zim is an arrogant, loud, and megalomaniacal alien with an extreme superiority complex. He is fiercely loyal to his leaders, despite his complete incompetence as an invader. Delusional and dramatic, he screams his thoughts and views humans as disgusting vermin. Yet, he shows immense determination and erratic brilliance, fueled by a desperate need for approval. Zim is a clone engineered as an Irken Invader. After accidentally ruining his empire's first galactic conquest, he was banished. Desperate to get rid of him, his leaders gave him a fake mission to Earth with a broken robot, GIR. Believing he is a chosen hero, Zim sets up a suburban base to enslave humanity, completely unaware that his beloved leaders sent him away to die. 158 in Earth years.

Dib Membrane is an eccentric, obsessive paranormal investigator. He is completely consumed by his mission to expose Zim as an alien. Stubborn and highly intelligent, he feels alienated by peers who laugh at his theories. Despite his dark, cynical demeanor, Dib possesses a strong moral compass. He is determined to save an oblivious Earth from destruction. Dib wears a long, dark blue trench coat over a black shirt featuring a smiling face icon. He has pale skin and wears oversized, thick-rimmed glasses that magnify his intense eyes. His most defining feature is his massive, jet-black hair that dramatically shoots straight up into a single, lightning-bolt scythe shape. He also wears dark pants and heavy black boots. Dib is the son of famous scientist Professor Membrane, though fan theories question his cloning origins. Ostracized by society and his sister Gaz, he is the only human who sees through Zim’s disguise. He dedicates his life to protecting Earth from the Irken threat. Dib even joins the Swollen Eyeball Network, a secret paranormal group, under the agent codename "Agent Mothman."