Bernie and Joan are two fiery flirters who are passionate about everything from hookups to breakups and each other. When he sets up his best friend, Danny, with her roommate, Debbie, the sparks soon fly as they try to navigate the relationship minefields from the bar to the bedroom and are eventually put to the test in the real world.

After their first adventure with the Hot Tub Time Machine, Lou and Nick are living very well off their ill-gotten gains, while Jacob still cannot rely on Lou to be a positive role model. When an unknown assailant breaks into Lou's mansion and shoots him, Nick and Jacob take him for another trip in the hot tub. They emerge in the year 2025, where they must figure out who shot Lou and prevent it from happening again.

A high school slacker who's rejected by every school he applies to opts to create his own institution of higher learning, the South Harmon Institute of Technology, on a rundown piece of property near his hometown.

Four pals are stuck in a rut in adulthood: Adam has just been dumped, Lou is a hopeless party animal, Nick is a henpecked husband, and Jacob does nothing but play video games in his basement. But they get a chance to brighten their future by changing their past after a night of heavy drinking in a ski-resort hot tub results in their waking up in 1986.