The troll dolls above the Rex Mars Atomic Discombobulator have a slight resemblance to Homer.
This episode was almost banned from American TV. At the time, writing an episode of a sitcom about homophobia and homosexuality was either not done or done as a very special dramatic episode, which wasn't the case here. It was only after a change in FOX management that the episode could air, but only if a few lines that were either too homophobic or too risque could be cut or modified per FOX's Standards and Broadcasting.
The scene where the broken gas pipe creates a bright flame has been cut in TV airings to avoid seizures.
According to Ron Hauge, the writer of the episode, it was originally titled "Bart Goes to Camp" but was renamed as the joke was too oblique.
This episode originally focused on Lisa being interested in things considered "campy" (B-movies, goofy toys, etc) and Bart getting into it to, only for Homer to think that Bart is going to end up a homosexual.
Todd Flanders enters Bart's lottery, even though gambling is a sin.
Bart puts twelve lottery balls into the dryer, but only seven children (including Bart) are shown in the basement.
Even if it shrank when washed, there is no way that Homer's Pin Pals shirt would fit John.
John didn't recognize Homer from the shirt.
When Homer enters the kitchen, there are four brown donuts on a plate on the counter. When he walks back from the coffeepot, there are only three donuts: one brown, one pink, and one yellow. Homer then grabs a chocolate donut, and the same three donuts are shown on the plate.
Despite Homer's homophobia in this episode, he didn't seem to mind being kissed by his gay secretary Karl in "Simpson and Delilah", doesn't notice (or care) that his coworker Smithers could be (and most likely is) gay for his boss, and was completely oblivious to the fact that he was in a lesbian bar in "Fear of Flying" (he only freaked out because the place didn't have a fire exit).
Marge criticizes Homer for his homophobia. In "Summer of 4 Ft. 2", she said "Girls, Lisa. Boys kiss girls." This implies that she is homophobic herself.
Homer seems to think that only straight people had been in the house before John visited. Waylon Smithers was in the Simpsons' house in two earlier episodes: "Brush With Greatness" and "King-Size Homer". Even if Homer didn't know that Smithers is gay, Marge or Lisa probably would have figured it out.
Marge, Bart, and Lisa say "Ooooh" when John shows them the plumbing supply shop. However, the "Ooooh" continues after they have closed their mouths.
When Homer confronts John in the kitchen, the clock jumps back from 9:05 to 8:00.
The robotic Santa Claus is smaller at the end of the episode. It is possible that John has two Santa robots of different sizes.