If Batman was a hallucination and never real, it would drastically change the landscape of the DC comic universe and the interpretation of the character by fans. The stories would be centered around the person experiencing the hallucination, possibly dealing with their mental health and belief in a vigilante crime fighter. The overall themes in the comics and the impact of the Batman mythology would change heavily, as they would be based on a character that doesn't exist, affecting other related characters, like the Joker and Robin, similarly. This interpretation might introduce discussions on the power of belief and the blurred line between reality and imagination in a person's mind.