Yes, that’s a Game Boy Color cartridge sporting the Wolfenstein 3D logo. It’s not just cosmetic, because a modder named Anders Granlund has built a playable version of the classic FPS for the ancient handheld console. To give you an idea of the degree of difficulty, Granlund designed and built a custom ARM-powered board to power the graphics, and built it into the cartridge. The final result is playable on any Game Boy Color.
Source: Anders Granlund