Plot summary
Marjorie is being honored as a Napa Valley "community hero" and her mistaken belief that Bonnie nominated her leads her in turn to ask Bonnie to be her presenter at the ceremony. Bonnie plans a roast -like speech, which Adam thinks is a very bad idea. At the gala, the group starts having some issues: Jill is feeling very queasy, Wendy's brave wearing of a strapless dress leads to an embarrassing nip-slip incident, and Tammy is bouncing between taking care of Jill and flirting with their party's handsome limo driver.
As a result, Marjorie is off taking care of her friends when Bonnie gets to the stage, and Bonnie ends up completely discarding her plan to roast Marjorie and instead speaks emotionally (and beautifully) about how good a person Marjorie is, and how she saved Bonnie's life and is the mother she never really had. Marjorie later learns this and ends up doubly touched when her son Jerry shows up late to the ceremony (he had car trouble) and tells Marjorie that he not only loves her as a mom but that he was the one who nominated her for the community hero award.
Jill discovers that her nausea was due to her being pregnant: she tells Andy and he's overjoyed for her and for him getting to be a dad. Tammy helps the limo guy drive everyone home, with chaotic results. Title meaning: The award that Marjorie is receiving, and the key to successful limo driving that Tammy is learning with some difficulty to get right.
Credits
Adapted from Wikipedia contributors, Mom season 8. HTML formatting and reference markers removed.