My friend, Katie, and I chose Cyndaquil and now we finished the game and were working together on the pokedex. I came up wih a plan to save the game, turn it off and start a new one and pick totodile/ chickorita and trade for some random weakling the other had. She loved the idea but then she said it wouldn't work because you have to save after a trade. Is this true? By the way in case the information is imporant, we were using the trade/battle room because neither of us has a friend code for Heartgold and Soulsilver.
I'm sorry but there is not really any way to do it.
Although you could just make eggs for each other, but you will also need a Ditto.
Good Luck!!! :D