I think coconut is the only mystery that we won't be able to solve. The details surrounding his "injustice" are extremely vague. All we know is this:
[list=]Coconut was once a man but was transformed into a coconut "unjustly" by someone.
To reverse his transformation two things must happen: The Darkness that binded the Truth for so many years must be defeated and Merlin must cast a spell using the last energy of the truth stone.
The spell will help someone else and indirectly release Coconut from his curse.[/list]
That's it. Coconut is an original character so I think whomever he is will be original too. Now I still believe the Coconut is pure of heart and not evil. Merlin's going to cast a spell which releases the curse, right? I think Merlin knows the difference between good and evil so he wouldn't cast an evil spell.
As for who it helps, that's an entirely different story. To answer this you need to ask yourself this question: Who needs help in Stupid Mario Brothers? Peach, Bowser, Kamek, Waluigi, Brock, and Donkey Kong have all received closure, so I'm counting them out. According to what Rich has stated, Daisy and Yoshi shouldn't be returning. Mario and Wario have fulfilled their destinies. Some people think Link needs help but I think that his story is done. Did anyone hear him when he said, "I am at peace now." If he's revived then it'll be "OMG He's killed!" to "Well he's gone." to "OMG Link Again!" to "Good, he's at peace now." to "Ugh, Link's alive? I thought he was at peace." I'm not saying that it's not a possibility, I'm just saying that I wouldn't like it.
So who's left? Gary, Ness, Merlin, Snake, Otacon, Ash, and Luigi. I can't think of any "help" that could be provided to Gary, Ness, Merlin, Snake, and Otacon. Ash possibly, he still has to complete his Pokedex... Luigi's last line "I feel sick" could go two ways: He was possed with an evil spirit or he became physically ill. If he's physcally ill then he needs some help. Other then that it's a real head-scratchier.