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Tear Jerker: The Fly
The 1986 Remake
The best test to see if your friend has a soul is whether or not he/she cries at the ending.
The "Insect Politics" scene.
Brundle: I'm saying... (finally reveals himself to Veronica, who fearfully steps backward) I'm saying I-I'm an insect... who dreamt he was a man... and loved it. But now the dream is over... and the insect is awake.
Veronica:(looking close to tears) No, no... No, Seth...
Brundle: I'm saying... I'll hurt you if you stay.
The Sequel to the Remake
When the boy protagonist of the sequel euthanized the deformed dog. To clarify, he saw this dog become horribly mutated in a failed teleportation experiment two years ago, and was told it had died. He finds the dog still alive two years later, clearly in huge pain and having to eat liquefied food, yet it's able to recognize him. Even sadder is that the protagonist pets him while he is whimpering, and what's left of its tail thumps the floor.