When Ned Flanders rents out a room, he has a "no pagans" sign. Religious intolerance is considered a sin in all Christian denominations.
When Homer catches Bart and Milhouse viewing the SexySlumberParty.com website, Bart's head is partially see-through.
In the church scene, Ruth Powers appears twice; Sarah Wiggum is shown, but there is no sign of her husband or son; and a Ned Flanders-lookalike (without sweater) is also seen in the last pew next to the wall.
In church Ned isn't wearing his suit and is wearing his usual clothes.
Even though this episode features sexual content, it is rated TV-PG. This is one of many examples of "Simpsons" episodes being incorrectly rated, with many episodes that should be rated TV-14 being put as TV-PG, usually with the incorrect content descriptors.
When everyone was at Ned’s house, Comic Book Guy’s skin is miscolored.