For me it will have to be on my pokemon gold.
I started with a Totadile and i captured about 3 other pokemon ( cant remember what they were ) and i totally forgot about them and i was just using Totadile all trough the game!
Hmmmm yep this has been done about ??????? times checks user profile yep even ive done this already but never the less if Pokemon where real then i would catch myself a grovile and that would do for me.