5th Gen You Can battle the NPCs you traded with.

In generation V, you can battle w/the NPC trainers you traded Pokemon with! This may be a small feature, but it's very endearing to see the NPC you traded Pokemon with is taking care of the Pokemon you gave to them. Did you know this is something in the games you could do? Did you ever battle the trade NPCs? I did, I know for sure I did, because the NPC that gives you either a Petlil/Cottonee is the one I battled once. They evolve your Pokemon, and the nickname is kept. It's pretty cute, honestly.