That cliché of zombies craving and eating human brains comes not from the George Romero masterpiece NIGHT OF THE LIVING DEAD or any of the follow-ups in the franchise. It began with THE RETURN OF THE LIVING DEAD. Gotta give credit where it is due. Romero invented the trope of zombie Horror. Everything that came after, all of it, couldn’t have happened without him. But it was Dan O’Bannon’s Horror-Comedy that invented the thing about brains, and also the thing where zombies can actually talk—typically just muttering “Braaaaaiiins…”
John Russo and George Romero collaborated on NIGHT OF THE LIVING DEAD. After the movie came out and the two parted company, both retained the rights to the zombie world that film had created. Russo could continue to use the title “living dead” but Romero could still use the zombies. This all came about due to the copyright flub that led to NIGHT OF THE LIVING DEAD becoming public domain. Russo went on to write a novel entitled RETURN OF THE LIVING DEAD. Dan O’Bannon agreed to direct the film version of that novel, THE RETURN OF THE LIVING DEAD, only if he could rework the script into a black comedy, because he didn’t want to rip off Romero’s idea. (Good for him.) Thus the film bears little resemblance to Russo’s book.