Sheldon and Leonard's mothers (guest stars Christine Branski and Laurie Metcalf) are coming to visit to see them win an award. While Sheldon is excited, Leonard is less than thrilled.

When the two mothers arrive, they butt heads over their fundamental beliefs, and Penny finds herself in the middle. Leonard's mom is a psychologist who does everything by the book, while Sheldon's mom has always offered Sheldon unconditional love.

Meanwhile, Bernadette comes home from running errands to find the guys still sitting around playing video games. Fed up, she convinces the guys to stop playing video games and clean the kitchen from to to bottom. Howard finds that task to be difficult, making more of a mess than there was to begin with.

Sheldon has coffee with Leonard's mom, and Sheldon explains how his mom raised him. Back at the apartment, Penny and Leonard talk with Sheldon's mom, who feels she still has to be a good Christian and apologize.

Leonard's mom arrives back to the apartment and  tries to be a different kind of mom, starting with trying to show Leonard affection.

Howard and the guys continue cleaning the kitchen, which they've proven to be pretty bad it. They start singing "It's a Hard Knock Life" as they clean.