There are two secret speed upgrades to the GB Tower Game Boy emulator that let you play Pokemon Red, Blue and Yellow at much higher speeds:

Doduo Mode: Beat the Poké Cup. Once you have won all the Poké Cup tournaments, the GB Tower changes into Doduo GB Tower and a Doduo sticker appears on the Game Boy. The Doduo upgrade doubles the speed of the game play when playing the Game Boy game on your N64.

Dodrio Mode: Play the Game Boy games at hyper speed with this alternate speed settings. To get it, you need to beat the Prime Cup (after you have already beaten the Poké Cup). You can switch between the different GB Tower speed settings during gameplay by pressing C Right.