"Milhouse of Sand and Fog" is the third episode of Season 17.
When Maggie comes down with the chicken pox, Homer actually takes some advice from Flanders and holds a "pox party" so his friends could have their kids infected. After one too many "Marge-aritas", Kirk and Luann van Houten plan to get back together. However, Milhouse realizes they are too interested in each other and not interested in him, so he tries to break them up by planting a bra in his parents' bedroom. One problem: Luann discovers that it is Marge's bra, which leads to Homer and Marge breaking up yet again.
Maggie comes down with chicken pox and Marge warns Homer not to touch her, as he has no childhood immunity. Homer is forced outside where Flanders asks if he can purposely expose the boys to the chicken pox. So Homer invites all the neighborhood kids over to the Simpson house for a "pox party" (at fifteen bucks a head). However, he ends up catching it himself. One good thing comes of it, however: Milhouse's parents reconcile, or so they think.
Milhouse feels neglected because his parents aren't fawning over him as they once did, competing for his love. With Bart's help, Milhouse schemes to break up his parents again. Using a plot borrowed from The O.C., The boys leave one of Marge's bra conspicuously located in Kirk's bed and Luann thinks that Marge is having an affair with her husband. Unfortunately, Homer thinks Marge is cheating on him and when he accuses her, an argument ensues, and Marge throws Homer out of the house. Bart realizes that he may have separated his own parents instead of Milhouse's parents.
Bart admits to Marge about what he did, but Marge refuses to let Homer come back since he doesn't trust her. Bart schemes to reunite them by tossing a dummy of himself off Springfield Gorge and into the river, but Milhouse's poor eyesight ruins the plan, and Bart ends up taking the plunge. Homer leaps into the rapids and saves Bart. As the two come to a waterfall, Bart confesses to Homer that he left the bra in the bed. Homer strangles Bart, and Marge leaps in and saves them from going over the edge of the falls. Once the trio are back on dry land, Homer and Marge reconcile. Milhouse, not wishing to live in a world without his best friend, leaps over the cliff. Marge worriedly questions if he can swim. "What do you think?" asks Bart.
Behind the Laughter
This is the first episode where Maggie has Chicken Pox.