This really amused me, so I wanted to share.
I've been trying to get a Xerneas pretty much since the game came out. I have Y, so obviously I can't get it within my own game, so I've been trying on GTS. Obviously pretty much all anyone wants on GTS is stuff that requires Pokemon Bank, which isn't here. Tried to use Axew to get it (which I had a LOT of luck with in Gen V. Pretty much any legendary I wanted could be obtained within a week with an Axew), but after a month I had no luck. Tried a Vivillion (sp?) cause I heard people collect the various kinds, but again no luck (either mine is common, I missed the boat, or there simply wasn't any interest). I finally said 'whatever' and just threw a Chansey on there because I figured it had as much of a chance as anything else. It was one I had gotten through a Wonder Trade, and it didn't have any special items or Pokerus or anything interesting.
Checked the GTS today to see if it was still there, and was informed that a trade had been made. Lo and behold, there was my level 62 Xerneas.
I will never understand people on the GTS.