After the fourth graders and fifth graders engage in a heated dodgeball battle, Bart discovers that one of the fifth graders has the same mysterious scar on his hand. Puzzled by the matching blemishes, Bart tries to understand why and how he got it, leading Marge to explain that seven years ago, she and her girlfriends formed the "The Cool Moms," a tight-knit group of moms who set playdates for their young boys. Inspired to reconnect with the women, Marge's social life soon becomes recharged, but when Bart's playdates stop being fun, he attempts to break up the club, and Marge finally remembers why she left the group in the first place. Blackboard: 'January is not Bart history month'.