MYSTERY GIFT

Mystery Gift is a function found on the Main Menu which lets you receive Pokemon and items from Nintendo, other games, etc.

Activating Mystery Gift
First go to the Jubilife TV Station.
On the second floor is a man standing next to a women and he will ask for a saying.
Reply with the words "EVERYONE HAPPY" and "WI-FI CONNECTION" and then Mystery Gift will appear on your starting menu.

Options Available
The "Get Via Wireless" function allows you to receive gifts from a wireless connection as long as you're in range, examples include Pokemon given away at department stores and Pokemon from Pokemon Battle Revolution.

The "Get From a Friend" option allows friends to share their gifts with each other, one example is the Secret Key in Pokemon Platinum.

Finally the "Get Via Nintendo WFC" option will be used when Nintendo place a Mystery Gift on Wi-Fi for people around the world to download as they've done with the Secret Key.