"The Four Legged Visitor"
A happy couple adopts a new puppy. Only, it’s not a puppy at all, but actually an alien.
[cuts to the dog being an alien]
The loving couple brings the dog home and the wife pours it some food, while the husband goes upstairs to fetch it a toy.
To the husbands shock, when he returns, he finds his wife being devoured at the neck.
He dashes upstairs and the dog follows suite - causing him to fall off a balcony where when he lands with his shin bone sticking out of his leg.
The dog tugs the bone out and walks happily back to the shelter.
Where it will soon be adopted again, by another loving couple.