I've been playing through my brother's LeafGreen version to get Mewtwo and noticed something interesting on Five Island. If you check the computer monitor in the rocket warehouse, you'll notice it says "The Influence of Magnetic Waves on Pokemon Evolution". In the 4th gen Magneton and Nosepass evolve under a strong magnetic field, like the one in Mt. Coronet. So maybe Diamond and Pearl were already being planned and this was a nod to them. More importantly, I wonder if there are any other references like this.