the title.

On Pokemon Stadium 1 and 2 (both N64) there is the GB tower, where you can play your Pokemon RBY (and in Stadium 2, GSC).

Note that Gameboy tower is banned for English runs, but not for Japanese runs

that's strange why is it banned for english runs?

The emulation is inaccurate, I think RNG is not emulated correctly, and also the timing might be wrong