Dan and Caroline Yoder think they've finally made it. Their daughter Molly - not the most diligent of students - somehow managed to graduate high school and get accepted into college. Her proud parents are breathing a heavy sigh of relief as they look forward to an empty nest. Across town, Molly's secret boyfriend, Junior Hernandez, is graduating from his high school with top honors and has plans to go to Stanford. Parents Miguel and Lisette are bursting with pride. Everything seems like it's falling into place for them, but unbeknownst to both families, Molly and Junior are about to become parents themselves.
Molly steals Junior away from his graduation party to talk with him about her pregnancy. She's freaking out, but... if she wanted this, would he be okay? Junior says of course and promises Molly she means more to him than anything else. He promises to do the right thing - which stirs up some of Molly's underlying feminist notions - but the subject quickly changes to their parents. They're going to have to tell them very soon.
Dan promises Caroline he'll get in shape in preparation for their empty nester renaissance. He hits the local boxing gym in hopes of kicking off a new workout regimen, but the owner of the place turns out to be a real jerk. The two get into a huge squabble about Dan bringing a drink into the facility, even though a sign clearly says NO FOOD OR DRINK! Dan vows never to return, completely unaware that the jerk he's fighting with is Miguel Hernandez... Junior's father!
At home, Molly awkwardly tells her parents about her boyfriend, Junior. Good for her! Also… um, she's pregnant. What?! Dan and Caroline freak out just as Junior and his parents ring the doorbell. When Dan opens the door, he can't help but say, "There are four million people in LA and this is the guy who's son knocked up Molly?!" Unfortunately, Junior couldn't bring himself to tell his parents yet. The room devolves into chaos.
Dan and Miguel trade barbs about each other's terrible parenting. Both sets of parents try to explain to their children how much they've screwed up their futures, but Junior and Molly already have a plan! He'll transfer to UCLA and teach test prep, and Molly... well, Molly will pierce ears at the mall or something. The next day, Junior visits Dan at his office and asks for Molly's hand in marriage. Impressed, Dan says yes. Junior rushes to propose to Molly, but when she finds out he asked her father for her hand, her feminist side rears its head again and she stomps off in a snit.
Molly goes to Miguel's gym to ask for Junior's hand in marriage - why should it be the male's decision? Miguel emphatically says no, which makes Dan all the more sour to his future in-law. Dan pays Miguel a visit at the Hernandez house and gives him a piece of his mind. Miguel apologizes for hurting Molly's feelings, but lets it be known that when someone marries a person, they're also marrying that person's family... and there is no way Junior is marrying Molly's family! Line crossed. As the parents start screaming at each other, Junior proposes to Molly again and finally gets a yes. Despite his father's reluctance, Junior says this is what he wants; if either family wants to be a part of it, then they can join Molly and him at the Santa Monica Pier to celebrate.
The Hernandezes and Yoders grudgingly join their children at the pier. Despite the festivities, it's clear Dan and Miguel just don't see eye to eye. But the families put differences aside when they hear Molly's about to ride the roller coaster - she can't do that if she's pregnant! Dan and Miguel race across the pier to stop the ride before it goes any further. But when the coaster stops, Molly shows up behind them. She was never on the ride! Minutes later, Miguel helps carry Dan off the pier, since he pulled his hamstring running to the coaster. That night, Dan starts to come around to the idea of his daughter's pregnancy. Sure, it could sidetrack the renaissance of his marriage, but it doesn't have to! Little does he know, Caroline's in the bathroom, staring down at her own positive pregnancy test...