I know that Mario and Luigi and all things related to them are copyrighted and strictly belong to Nintendo. BUT, my son is seriously into Super Mario Brothers for the Wii right now. It's all he talks about and wants to do. We have to limit him, because he would play all day if we'd let him.
So, I am on the hunt for a kit that is done in primary colors and features things like cute little mushrooms, turtles, square bricks, clouds, flags, coins, yellow stars, a grey castle, etc. Like I said, I know that actual Nintendo items cannot be included, but I would think that a kit "inspired" by it would not cause any infringement problems. The kit could also include general gaming things like a T.V., controller, etc.
I'm not the only one on the hunt for such a kit. Almost everytime I look at the ISO thread at DST, someone is looking for a Super Mario kit. So I think a designer could really find a target market with this.