After Rebecca tells Dave she carries the emotional labor, aka the "mental load" of the family, he tries to prove otherwise by having her take care of just Deb and Stew for a few days. They both realize they've bit off more than they can chew, especially when Dave enlists his mom to help with Rebecca's mental load. 

Dave and Rebecca are worried that with grandparents living in the house, their kids are too spoiled. When Asher loses his first tooth, Deb and Stew interfere with the tooth fairy and prove Dave and Rebecca right. Joanna lies to her new girlfriend about being a much more involved aunt than she actually is.