And we had limited lives and continues and couldn't save our games! And Luigi was just a green-coloured Mario and we liked it that way!
*grumble grumble*
Actually, scratch that last part. Though Luigi's name is supposed to sound like "ruiji", which is like Japanese for "clone" or "twin" or something, which made more sense when they were twins. Go check Wikipedia. Donkey Kong, Mario, Luigi, Wario, Waluigi, Link, Zelda, and Kirby all have interesting origins for their names, some of them having double meanings or two possible origins which are kind of neat.