*CUT TO THE CHASE*
NOTE: This spoiler was submitted by Jeremy
The film opens in Seoul, South Korea. A little girl and her mother are walking through a park for the girl's doll. After she finds the doll, lightning strikes in the sky. A giant monster manifests out of thin air and begins walking through the city. The little girl screams in horror.
25 years later, we meet Gloria (Anne Hathaway) coming home early in the morning while hungover. She tries to explain her situation to her boyfriend Tim (Dan Stevens), but he's had enough of her coming home at odd hours drunk and not being able to hold a job. He tells her he's packed up her things and that he wants her out of there. Tim leaves Gloria sitting there in disbelief. After he's gone, some of her friends come into the apartment to start partying.
Gloria moves from the city to her old hometown into her parents' old home. While walking home with an inflatable mattress, she is spotted on the street by her old childhood friend Oscar (Jason Sudeikis). They catch up and he invites her to join him at the bar that he inherited from his father. There, Gloria meets Oscar's other friends Garth (Tim Blake Nelson) and Joel (Austin Stowell), the latter whom Gloria finds attractive. The four of them drink in a part of the bar that Gloria remembers from a while ago as it has horses painted on the walls. Joel attempts to kiss Gloria at one point, but she pulls back as Oscar yells at Joel.
Gloria walks home drunk while hauling the mattress in a bag across her back. She passes through the park and over the playground.
When Gloria wakes up, she gets a call from her sister to check out the news. Gloria opens her laptop and sees an article and video of a monster attack in Seoul. She is horrified to see this. She calls Tim about what she saw, but he knows she's been drinking and he doesn't want to talk to her in that condition.
Oscar gives Gloria a job to work at the bar and even gives her a big TV for her living room. She spends her time drinking and hanging out with Oscar and his buddies again. She goes home drunk through the park again.
Gloria wakes up and sees that the monster reappeared in Seoul. Oscar shows up at her house as she is seeing this on the news. He comforts her as she is still freaked out, but as Gloria looks at the TV, she sees that the monster is scratching its head, which is something Gloria did earlier that she identifies as a tic where she constantly scratches her head. When Gloria looks further into the footage of the monster, she sees that it looks as if it is carrying something on its back.
Gloria goes by the park around the same time that the monster was reported to start attacking. She lifts one arm up in the air and then raises both arms. When she sees the news later, the monster has mimicked her exact same movements.
Gloria brings Oscar, Garth, and Joel by the park around 8:05, which is the time that the monster usually starts to emerge. The guys pull up livestream sites that record the monster as it appears. Gloria then starts dancing, and the monster starts doing the same moves. After a while, the guys notice what's going on. Joel thinks it's a prank but the monster still does what Gloria does. They inform her that helicopters are shooting missiles at the monster, which physically affects Gloria as well. She makes punching gestures, making the monster punch the helicopter and causing it to crash against its head. Gloria then stumbles drunkenly and falls.
The news then shows that the monster's fall caused serious destruction and killed hundreds of people. Gloria becomes distraught and guilt-ridden. Oscar goes to her house and brings her a newspaper showing that the monster was joined in the city by a giant robot, which Oscar thinks is him.
While Gloria is still freaked out by having indirectly killed people, Oscar isn't too bothered by being a robot. With his help, they find a Korean man who helps them translate message. Gloria goes by the park and makes the people of Seoul step away from the monster as she/it begins to write a message into the ground. The message translates to "I'm sorry, it was a mistake, it won't happen again." The opinion on the monster changes, now having people believe it means well.
Gloria goes over to Joel's place where they hook up and she spends the night.
Gloria and Oscar get drunk and then go to the park again. As both the monster and robot, Gloria slaps Oscar, making it look like the monster and robot are fighting. The monster appears to order the robot to leave, and the people of Seoul cheer on the monster.
Gloria starts to do better by not drinking so much. However, Oscar starts to seem more hostile and antagonistic as he drinks. He tells Gloria to have a beer, and she refuses until he says he will go to the park if she doesn't take it. She takes the beer and pours it out in front of him. Oscar also calls out Garth for doing cocaine in the bathroom. Oscar then leaves drunkenly as Gloria goes after him.
The next day, Joel comes over with a bunch of furniture for Gloria's house that Oscar sent as an apology.
Tim contacts Gloria. She visits him at a Holiday Inn. They argue when Gloria mentions she's working at the bar, even though Tim previously dumped her for losing her last job. They later go to the bar where Oscar is already drunk and being a dick with customers. He takes out a massive firework that he and his friends bought long ago and were saving for a special occasion. The other patrons clear out as Oscar lights it, sending fireworks everywhere.
Through a flashback, we see Gloria and Oscar as children on the way to school with models they made for class projects. The wind blows them away out of their hands. Oscar goes into the woods and finds Gloria's model, but he starts stomping on it spitefully. Lightning then strikes in the air, hitting both children in the head. Out of their bags spill toys that resemble the monster and the robot.
Gloria goes home later to find Oscar in her house with keys that her parents gave her years earlier. Gloria tells Oscar that she figures his behavior comes from the fact that he hates himself. They start fighting and destroying furniture until Oscar runs out. Gloria follows Oscar as he goes to the park. She tries to stop him, leading to another monster-robot fight in Seoul. However, Oscar starts to strike Gloria, eventually knocking her down. He tells her that if she leaves, he will continue to rampage through the city. As he stomps around the park, we hear the sounds of people in Seoul screaming in terror as the robot stomps through the city, while Gloria lies helpless on the ground.
Gloria then gets an idea of how to stop this. She takes a plane to Seoul as the city is being evacuated. She gets a call from Tim asking if he's going to go back with her. Gloria says no and hangs up on him. Meanwhile, Oscar is drunk and walking into the park, so the robot materializes over the city. The people run from it but Gloria walks toward it. In the park, Oscar hears stomping noises as the ground shakes. The monster is now standing over him. He runs away in terror, and the robot runs across the ocean. Gloria moves forward and grabs the air, which makes the monster grab Oscar and makes it look like the robot is being picked up by an invisible force. Oscar starts crying and yells at the monster to put him down. He calls her a fucking bitch, so Gloria/the monster hurl Oscar/the robot into the distance. The people of Seoul cheer as the robot is gone.
Gloria walks away from the scene. As it is being reported on, Joel sees her on TV behind the anchorwoman commentating on the scene. Gloria walks into a small restaurant, looking like she's about to cry. The woman behind the counter asks if she wants food. Gloria says yes, and then offers to tell the woman a story. The woman agrees and then asks Gloria if she wants a drink. Gloria just sighs.