Now here are the rules for the Story.
First off as stated in the First episode only particular "Episodes" (The parts that you write) can go in particular places. The most leaninent is the "With Author Insertions" to the most stringent "Nintendo Only".
Next off this site is to be family friendly. Which basicly means No Adult or Vulgar material is to be posted.
Next off when making links to other episodes make sure that you are giving your reader some options. Giving Mario the choice to go to the left or right is not very creative. Try to make your links more creative like
Does Mario go to the left where there is an odd light or to the right where he spoted some one dash around the courner?
That works because it's giving the reader (and writer) more to go by when making a choice through the story.
Next, Episodes must be relivent to the episodes prior to it. Don't suddenly change the plot at least with out explination.
Also Longer Episodes are a million times better then one sentence episodes. That is not to say that One sentencers are not possible or have a chance of being good, However the general chances of that are slim to none. Please put details into the story.
As far as who's perspective the story is taken from I really couldn't care less. it doesn't just have to be Mario's. Just keep in mind that this is to be a Mario based story.
Cameos from other games such as Link are okay by me. Just don't go turning this into a Pokémon story or a Zelda story etc...