Lisa breaks Ralph's heart

S06E03 - Another Simpsons Clip Show

Marge is reading a book one night and wakes up Homer to ask if he thinks the romance has gone out of their marriage. Homer ignores her and tosses the book into the fireplace.

In the morning, Marge gets the family together to discuss romance, but they can only come up with vignettes from their failed relationships in the form of clips from previous episodes. Homer, however, saves the day when he brings up how he and Marge got together. Ultimately, the kids do not care for this one and wind up watching Itchy & Scratchy while Homer and Marge share a moment together.

Source: Wikipedia