I don't have this game, but I do intend on getting it. Anyway, if I want to make a game with Mario characters, how could I keep it from being deleted? Do I have to make a staff credits and put Nintendo in it, or on the title screen, or something like that? That you! Bye!

Well, the simplest way to avoid getting a takedown for copyright is simply NOT use copyrighted assets. Of course, you could also declare your work as a parody or just a work that uses these assets under what could be considered fair use. Now, determining what is considered fair use is a bit of a gray area, and even then, you would have to give the appropriate credits to the original creators.

Also, it must be made clear that remaking games or making games that use more than just the intellectual property of these creators, such as music and/or gameplay, is usually not regarded as fair use of the assets and is most likely to be taken down. As such, you should limit yourself to using assets in a way that's tasteful and simple. For example, you shouldn't just remake a Mario game.

I meant to make a new one, with difrerent boards and stuff.

That's fine because you can call it a ROM hack.

@Brandon Won't That Make It Get Taken Down Faster?

Some people say that you can do ROM hacks or bootlegs on there, but I wouldn't request it for miiverse rules and illegal stuff. :,)

Your fine if you dont post it or sell it,but I'm pretty sure you can't do that one here anyways.