Gaist Crusher is an upcoming 3DS game from Capcom and Treasure of Sin & Punishment and Ikaruga fame. Gaist Crusher is aimed at kids. And it has one strange-looking add-on.
See that? That's a special cover that players can use to attach various "Gai Metals" to their 3DS. Each Gai Metal can transform into various creatures, but once attached to the 3DS, it gives players special in-game gear.
This is an optional add-on, but Capcom is probably hoping little kids will start collecting these various Gai Metals, which they might. But geez, they make the 3DS look somewhat ridiculous.
Gaist Crusher is slated for a December release in Japan.