When Bart discovers that a fifth grader has a scar identical to one Bart has, Marge tells him about a club of four mothers she was in seven years earlier; when Marge plans to reunite with the mothers, while Homer reunites with the fathers and Bart with the boys, matters turn out much better for Marge than for Homer or Bart, who, after hearing the story from Jeffery Albertson about how they got their scars, tries to break the group up.
The episode opens with a dodge ball match between the fourth and fifth graders. Bart ends up hitting the last last fifth grader. However, Erik catches the ball after it comes back down, making the fifth graders win the match.
In the days that follow, the fourth graders harass the fifth graders to the point that they organize a fight after school. Before the fight begins, Bart observes that Erik has a scar on his fist, which is identical to one that he has.
Bart confronts Marge about the scar. Marge explains that when he was in preschool, he was in a "Mommy and Me class" with three other kids. Marge became very close with the other mothers, and they became "the Cool Moms." However, the other kids were a bad influence on Bart. Marge then chooses to get back together with her old group.
Marge's old friends reconcile while Bart gets together with the other kids, where he realizes he still does not know where the scar came from. Marge and her friends chose to get together every Tuesday. Meeting with the other kids every week, their antics become more and more dangerous, so Bart plans to separate the group. Knowing they broke up before, Bart realizes it must have something to do with the scar and consults Dr. Hibbert, who suggests he ask Jeffery Albertson. Albertson then reveals what happened: About seven years earlier, on the fourth of July, he was in charge of the fireworks. While Marge and the other mothers discussed this, Bart and the boys stumbled off towards the fireworks controls and pressed all the buttons, setting off all the fireworks. In the fiery explosion that followed, Albertson's sandwich was struck by a flaming ball, sending the burning hot skewers onto the boys' fists, branding them.
Realizing that it was an explosion that split them apart, Bart and Milhouse create a big ball of fireworks to break them up again. When Marge catches them in the act, Bart confesses. That evening, Marge tells the group of Bart's scheme to break them up, and they tell her Bart was always a bad influence to their kids. Marge becomes frustrated and leaves the group. Afterwards, the women start making out with each other.
This episode reveals the reason why Ralph Wiggum is mentally challenged, this is due to getting dropped on his head by his father as a baby.
The episode's title, “Moms I’d Like to Forget”, parodies and shares the same acronym as "MILF", meaning "Mom I'd Like to F*ck", a profane term for a sexually attractive mother.