The Simpsons' fourth season features an interesting Ned Flanders plot hole centering on his church attendance. Since the show's first full-length episode, Flanders has been a constant background player, characterized by his one-side friendship with Homer and his staunch evangelical Christian faith. Both of these aspects of Ned Flanders' character are at play in the season 4 episode "Homer the Heretic."
The core of the episode is Homer's disdain for going to church on Sunday mornings, preferring to stay at home and watch television. After opting not to attend, he begins to enjoy life at home while the rest of the family attends Sunday services, and following a dream in which he and God make a deal that Homer can be a good, kind person at home without going to church, Homer continues to refuse to attend despite his family and friends' urging - including persistent pursuits from Flanders.
While the rest of the family is away at church, Homer accidentally starts a house fire, and he passes out from smoke inhalation with no one around to help him. Flanders notices the house engulfed in flames and arrives to rescue Homer. But why was Ned Flanders not at church with his wife and kids and the rest of the Springfield community? Given his commitment to his religion, Flanders should be the last person around to help.
This may be attributed to the time at which Flanders attends. Despite the fact that he is seen attending church with the rest of the community when Homer first decides not to go, it's possible that Flanders went to an earlier service when Homer's house caught fire. Considering how much Flanders values his time with the Lord, this explanation is shaky at best, and the most likely explanation is that Flanders' miraculous availability is a plot hole. Even during the series' golden years, it was not perfectly written at all times, and over its remarkable history a few Simpsons plot holes have popped up.
The conclusion of The Simpsons episode "Homer the Heretic" offers no explanation for why Flanders was home at the time, but it does end poetically: after Homer's rejection of Christianity, his life was saved by a devout follower, Ned Flanders, and Homer returns to church the next Sunday, sleeping through the service and having another dream about meeting God.