It's best to ask for a Lv.9- Mothim, or something equally impossible, as hackers can obtain any Pokémon of any level to steal your GTS-exploiting Pokémon, and they very much enjoy doing so, as people often clone their shinies, legendaries, or rare items like Master Balls and one-time TMs.
EDIT: Removed my mistakes, and I evolved my Rhyperior using this trick! Unfortunately, I lost one of my Deoxys in the process (who trades a Lv.7 Wurmple for a Deoxys of any level?!), but it was just an extra, so it's an acceptable loss.