So I've been playing Platinum lately (I know guys pretty old school) and I've come across something on the Internet about being able to trade on GTS to evolve without actually trading your Pokemon away. I was hoping someone could confirm that the method actually works and is reliable.
Trade evolution glitch
In Generation IV there is a glitch with the GTS that allows Pokémon to evolve by being traded, but without actually trading them. Players must first place a Pokémon that evolves by trading it (with the correct held item, like Metal Coat for Scyther or Electirizer for Electabuzz) onto the GTS. To prevent the deposited Pokémon from being traded away, players should request an impossible trade, such as a level 9 and under Mewtwo.
The player must then search for a Pokémon on the GTS and trade for it. After this has been done, returning to the Pokémon that was placed on the GTS by the player and taking it back will cause it to evolve.
It is possible that this was intentional, however due to the fact that it was removed in Generation V makes this very unlikely. The risk of not being able to reacquire a Pokémon while trying to evolve it through trade evolution over the GTS is very great and this could have been a planned countermeasure. The requirement (a trade) must still be met in order for the Pokémon to evolve, but this system would prevent a player from potentially losing the Pokémon they wanted to evolve.
Thanks guys! :D