Mr. Smithers has a severe and almost instant allergic reaction to a single bee sting, which he claims "cause him to die." However, in the season 3 episode "Burns Verkaufen der Kraftwerk," when visiting Mr. Burns while he is beekeeping, he mentions that several bees are stinging him, but with no apparent ill effect.
Superintendent Chalmers takes a bite out of a burger, but when he shows Principal Skinner that it's clearly grilled it's whole again.
When Skinner brings out his plate of hamburgers, there are four burgers on the plate surrounded by fries, but when Chalmers takes the first bite out of a burger, two of the burgers are suddenly gone from the plate along with half of the fries.
Waylon Smithers in one episode claims to be getting stung by bees, however in other, when stung, he has an allergic reactions and claims he is allergic to bee stings.
When Marge first attempts to remove the gum from Lisa's hair she adds the peanut butter then the mayonnaise, but in later scenes the peanut butter is on top.
When Jake cuts the gum out of Lisa's hair and leaves a bald patch, she reacts before he holds up the mirror for her to see the difference. The same happens after he restyles her hair.
Lisa complains that her scalp hurts from horsefly bites, but the insects that descended on her earlier were bees.