Lost Levels: How do you switch between Mario and Luigi?


I've just started playing Lost Levels on the Wii Virtual Console, and aside from at the start of the game, I don't see where I have the option to switch between Mario and Luigi?? Do I just have to pick either Mario or Luigi and use them the whole game? Can I not switch before each level? I thought I read somewhere you could switch when you die, but I don't see that option. When I die it just gives me the option to continue.
You can't switch. The only way to do that is to reset the game.
Yeah, Luigi is a little bit easier, because of his high jumps. That makes it a lot easier to cross large gaps. The only problem with Luigi, however, is the fact that he has less traction than Mario.