You can apparently choose how Eevee evolves in Pokemon GO

Eevee is one of many Pokemon to be found in Pokemon GO. However, it can evolve into one of three creatures: Jolteon, Vaporeon, and Flareon.

Choosing your Eevee evolution is actually rather simple. For Jolteon, simply give your Eevee the nickname Sparky. For Vaporeon, name it Rainer. Choose Pyro to nab Flareon.

Here’s a look at the trick in action:

As for where these nicknames came about, the Eevee Brothers from the original anime were named Rainer, Pyro, Sparky who owned a Vaporeon, Flareon and Jolteon respectively.

Source, Via