I used to play GBA games at home with the Game Boy Player accessory for the Nintendo Gamecube. It connects to the bottom of the GameCube, adding a base to it. Is there any way that it could be connected to the Nintendo Wii?
No, a Game Boy Player is not compatible with the Wii directly, as the Wii lacks the required Hi-Speed port availble on the Gamecube.
However, the Game Boy Player in combination with a Gamecube and a Seperate TV, is still a valid (but highly impractical) controller for the Gamecube and Wii games that support the GBA as controller.