Ketchup and fries go hand in hand like, ... well, how about potato and tomato?
Meet the "Ketchup 'N' Fries" pomato or tomtato (previously on Neatorama), a chimera plant made from grafting a potato and tomato plant together. It is available from the Territorial Seed Company of Oregon. Above the ground, the plant is a cherry tomato plant, whereas below the ground you'll find white potatoes.
The website states that this kind of frankenplant grafting is possible because both potato and tomato belong to the Solanaceae (nightshade) family.