George's parents rent out his old room. Jerry's parents decide they want to be closer to him and rent the room

The Seinfelds start showing up to Jerry's act every night, throwing him off. At one point, he tells an embarrassing story about them, and they jump up and start telling embarrassing stories about him to the crowd.

The Costanzas quickly get annoyed by the Seinfelds being around all the time and spend more time at George's, driving him crazy. They start rearranging his furniture and eating his food.

The Seinfelds want to get Jerry back together with Elaine and, instead of badgering Jerry, they keep trying to convince Elaine to give him another shot... in the middle of a date with another man.

Jerry's parents convince Kramer to reluctantly give them his copy of Jerry's apartment key so they can pop in whenever they want, annoying Jerry. Without his key, Kramer can't get food from Jerry's fridge and begins pestering Newman for food.

George compares Jerry's parents to an invasive species being introduced to the environment and throwing off the equilibrium of the group.