In S1E6, Jackson reveals that he has successfully created a raspberry/kumquat hybrid using cross pollination. Lorelai asks, “You didn’t build one of those machines like in ‘The Fly,’ did you? We’re not going to find you wandering the streets with a raspberry head, crying, ‘eat me?'”
“The Fly” is a short story that was first published in 1957 in a Playboy magazine. It was made into a movie in 1958 and remade in 1986, although the remake does not specifically feature a man with a fly’s head, so Lorelai was likely referring to the original story or the 1958 film.
In the story, a man creates a teleportation device, but a fly gets caught in the device when he’s testing it on himself. As a result, the man’s head and one of his arms get switched with the head and leg of a fly (but human-sized). The man works to fix himself for a while, but when he realizes that his brain is slowly turning into the brain of a fly, he convinces his wife to kill him.