The agreement between a couple when they get a dog to determine, if the couple should split, who gets residential custody of said pet.
John and Sherry just got a labrador retriever, but she made him sign a pre-pup in case they ever broke up.
Formal agreement between partners before they add a dog to the family.
Man: Well, if we ever decide to get a dog, we're going to have to sign a pre-pup first.
Woman: Yeah — Cuz if you ever break up with me, you'll never see that bitch again.
Man: Fine! But if she swallows some magnets and needs $1,500 in x-rays and surgery, she's getting the needle — and you'll never see that bitch again. That's the Darwin Award clause.