"With Donkey Kong, we have this gorilla who grabs this gal and runs away with her and you have to go chase the gorilla down to save the lady. And the game's stage was a construction site, so we made him into basically a carpenter. …. With (1983's) Mario Bros., we brought in Luigi and a lot of the game was played underground so we made him to fit that setting and, we decided he could be a plumber. The scenario dictates his role."
This video will give beginners a feel for the game, how to catch Pokémon, and how to advance levels. Hope it helps!