On a rare occasion, Lisa is seen eating meat after the Season 7 episode Lisa The Vegetarian, but that only happened on Homer's dream inside Marge's dream, so this could be considered as non-canon.
At the pharmacy, Homer sleeps hugging a toy octopus the same way he slept underwater in one of the family vacation photos.
This is the first time that Maggie Simpson has ever sung a song. The song she sung was What a Wonderful World. However, this happened in Homer's dream, so it's technically non-canon.
This episode can be non-canon due to the ending being a tatoo illustration.
At Moe's Tavern, when Homer, Lenny and Carl are watching the Itchy and Scratchy Show and discussing about Homer's relationship, the pickled eggs jar is nowhere to be seen, only appearing when Barney plunges the comb onto it.