When an Eevee is exposed to a Water Stone (or a powerful water-oriented magical event) it becomes a Vaporeon, a wet and fish-like Eevee composite that has a number of water powers and swims very well. Under other circumstances, an Eevee becomes immolated in flames and takes the fire aspect into itself. Regardless of how it transforms, an Eevee’s primary evolution is one-way and one time only. An Eevee who becomes a Vaporeon will never become an Espeon, and vice versa. Regardless of how it transforms, however, an evolved Eevee is still an Eevee. It remembers everything that happened to it while it was an ordinary Eevee, and can even mate with other Eevee forms, evolved or not. The offspring of such unions are always unevolved Eevees.