Time to Return the Favor

I'll choose Charmander. You thinking about how he did help you when you were out looking out for Professor Oak. Also he is the strongest of the three.

"Be warned he is the strongest, yet hardest to train." warns Professor Oak.

"It doesn't matter, he saved me and I trust with his firey passion we can win any battle." you gleefuly say.

Your rival of course takes Squirtle just to make sure his Pokemon can always beat yours. As you are about to leave the lab after thanking Professor Oak, your rival challenges you to a battle.