Part 1: Someone, we don't know who is.

what's going on in the mushroom kingdom?

A mysterious new soul or person .

The protagonists are: SMG4 and SMG3

This mysterious new human/soul is making all the characters in the Mushroom Kingdom creepy, why will he/she do it?

SMG4 and SMG3 will find out. . . . .

( This identity is trying to get SMG3, for something or not to bring it back, What will happen if SMG3 disappears ? )