>The SlowpokeTail is actually a useless item with no function past its monetary value. Although it is said that a Slowpoke will use its tail for fishing, a SlowpokeTail has no effect on fishing at all, nor does it have any effect on Shellder despite the fact that contact with a Slowpoke's tail usually induces a spiral change.
>The first time that humans eating Pokémon is mentioned explicitly in the games is when a Team Rocket member mentions the SlowpokeTail's value as a delicacy. In Pokémon X and Y, Slowpoke Tail is one of the dishes served by Restaurant Le Yeah in Lumiose City.
So, it does actually have a use! Only if you are a binary piece of code inserted by a bored GameFreak Developer, and you just happen to be transported from Johto to Kalos on a Porygon. improbable, but possible, and I trust you enough to pull it off. Mother of shenanigans, eh? Oh, did I mention, that it would be an added bonus if you're an ex Rocket Member. Take that Giovanni! Your worth would exceed the joint worth of Silph Co, and Devon Corporations, provided you do manage the Porygon, without, uh, getting seizures.