Pokemon Brilliant Diamond and Shining Pearl players are able to collect a few statues from the Mystery Gift feature.
These decorative statues can be put in a trainer's base in the Grand Underground of Pokemon Brilliant Diamond and Shining Pearl. Just put in the code and you'll receive statues of the Sinnoh region's starters.
Even better, these statues are of the Shiny variety. You can put them in your Grand Underground base once they are received. Entering the code BDSPUNDERGR0UND will add them to your collection.
How to access the Mystery Gift feature in Pokemon Brilliant Diamond and Shining Pearl
The Mystery Gift feature in Pokemon Brilliant Diamond and Shining Pearl can be found in the X menu. However, it will be missing until you get through a certain part of the game and its story.
You will need to beat Maylene, the Veilstone City Gym Leader, and her Fighting-type partners. Once you have done so, you will see the Mystery Gift option available when you hit the X button.
Enter the Mystery Gift feature and select "Get with Code/Password." Enter the BDSPUNDERGR0UND and wait for the spectacle to complete. Note that the "O" in the code is a zero.
How to place the Mystery gift statues
To place the statues and see them in all their glory, you will need to unlock access to the Grand Underground in Pokemon Brilliant Diamond and Shining Pearl. This can be done once you reach Eterna City.
Visit the house next to the Pokemon Center to find the Underground Man. Speak with him and he will show you how the Grand Underground works. Talk to him a couple more times for missions that will reward other useful items.
One of those is the Digging Drill. When in the Grand Underground, face any wall and press A. This will use up the Digging Drill and burrow a deep hole that will become the Secret Base.
After you have created a Secret Base, go inside and you can place the starter Pokemon's statues. Each statue will increase the encounter route of that Pokemon in a Hideaway, but it is unknown if it affects Shiny odds.