okay, maybe this is a bit of a stretch, but I was playing Soul Silver last night and in game I had chosen Cyndaquil as my starter. as such, my rival chose Totodile.
Now, remember in the beginning when you go back to Elm's lab and your character wonders where the 3rd pokemon (Chikorita, in my case) went? well, I went to Vermillion City and in one of the houses, there was a girl with a Bayleaf running around her.
my WMG? she was the one who Elm gave Chikorita to, though I'm not sure why.