George Stacy was the police captain of the NYPD and was Gwen Stacy's father.
When Peter Parker begins hunting down Uncle Ben's killer and making himself known to the public, Stacy immediately dislikes the mysterious costumed crimefighter. Captain Stacy was the man leading the investigation into Spider-Man's vigilantism. However, too eager to capture and put Spider-Man behind bars, he does not believe that Dr. Curt Connors has been turned into a giant lizard. His daughter starts to date Peter Parker, a boy going to her school. He and Peter got into an argument while eating dinner at the Stacy home. Peter believed that Spider-Man was helping the police and beinging criminals to justice while George believed him to be nothing more than a masked vigilante. This caused Peter to leave the house because he felt the Captain was slandering Spider-Man's name. After Spider-Man saves the lives of several people and fights off the Lizard on the bridge, Stacy's hatred toward Spider-Man remains undeterred, and the next morning, he issues an arrest warrant for "the masked vigilante known as 'Spider-Man'." He continually gets New York's finest police officers to go after him, but to no avail.
The next day, Peter arrives at the NYPD headquarters and informs Captain Stacy that Dr. Curt Connors is the lizard-creature that started the attack on the bridge and is going to turn all of New York into powerful man-lizards, and that Stacy has to stop him. However, Stacy, who was already disapproving of Peter from the night before, has the cops escort him out of the building, refusing to believe what Peter says. However, after contemplating it, he reluctantly has an officer run everything they have on file about Connors.
That night, Lizard launches a biological attack on New York City, and while Stacy orders a squad to stop it, Stacy himself instead personally leads a chase on Spider-Man. When Spider-Man is caught in the sight of the police, Stacy's helicopter stuns Spider-Man out of the air. The cops put Spider-Man in handcuffs, but when Stacy pulls off his mask, Spider-Man quickly beats up the cops and is about to escape until Stacy gets up and holds him at gunpoint, forcing Spider-Man to freeze. Realizing the situation, Spider-Man turns around and reveals himself to be Peter Parker. Stunned, Stacy is taken back by the revelation, but Peter convinces him that he has to stop the Lizard before it reaches Oscorp where Gwen is, and Stacy reluctantly lets him go. He then heads over to Oscorp, where he runs into Gwen. He reveals to her that he knows about her boyfriend's secret, and she gives him an antidote that will cure the lizard toxin and pleads him to make sure Peter's okay.
Eventually, Stacy somehow makes it near the top of Oscorp Tower and assists Spider-Man in defeating the Lizard. He gives Peter the antidote from Gwen and buys him time by fighting the Lizard himself. While Peter goes to switch the lizard toxin with the antidote, Stacy fires his shotgun repeatedly at Lizard, but the monstrous reptile quickly heals from his wounds and drives his sharp claws into Captain Stacy's chest, mortally wounding him. After Peter defeats the Lizard, Peter runs over to check on the dying captain. Stacy admitted that he was wrong about Peter and that city does need him. He warns Peter that with being a superhero, he will make enemies and that people (sometimes closest to him) will get hurt. Before he dies, he made one final request to Peter: to keep Gwen out of it for her own safety. Peter initially agrees to it, and watches sadly as the captain sucuumbs to his injuries.
Later, Stacy has a funeral where he is honored for his work as New York's top cop, and Gwen notes that everyone, even Flash, shows up, except for Peter. She arrives at his apartment, and Peter tells her that he can no longer be with her, and she realizes that her dad made him promise that. The next day in school, the two sadly ignore each other, until, in class, the teacher scolds Peter for being late, and when he says it won't happen again, she tells him not to making promises he cannot keep. Sitting behind Gwen, Peter quietly and slyly replies, "Yeah, but those are the best kind," which causes Gwen to smile, meaning that, for better or worse, Peter is going to stop honoring his promise to Captain Stacy and start dating Gwen again.
