Where do you get the mystery gift?
You can get the Mystery Gift from different sources, in the GBA
games it is a Survey within the PokeMart. In Diamond, Pearl and
Platinum, You must go the the 3rd Floor of the Jubilife City TV
Station and talk to the fellow with the beard and glasses. He will
ask you your opinion on TV. You must tell him the phrases
"Everyone" and "Happy". Then, when he asks the next question, you
must tell him "WiFi" and "Connection" He will be surprised, say
that your a trainer and tell you to save the game. Save the game.
If you want to access your Mystery Gift, turn the gave off AFTER
SAVING and go to the title screen, under your current game file and
the "New Game" option you should see the choice "Mystery Gift."
Once you have a chance, get something from the mystery gift.