The problem is that is just wasn't funny.
I think visually it looked fantastic. As mentioned before it says Vote for Peach and then it is later changed to Summer. You had some of the movie's songs on there that definately helped set the mood. Only place I really saw humor was the part about "you got my back" but it was very hard to find the humor with in my opinion the poor voice actor of 'Napoleon Toadamite'. I am unsure but I am assuming that it was altered from the original person's voice by some kind of program. It sounds nothing like that of the original Napoleon. I would suggest looking either for another voice actor or sounds from the actual movie. I am unsure if there are any lines in there that aren't said in the movie so I don't know if you could actually just take them from the movie. With that I think his actual voice is the reason why there is no humor in this. I don't think Bowser looked all that great and his voice actor wasn't that fantastic either. I do think Pedro did fine. I thought you were going to put Peach and Luigi handing out for vote for Summer because I do recall another guy handing out pages/pins and there was a scene with that. Maybe add something about Napoleon's brother and the internet conversation.
Other reviewers have no right to vote the way they are just for the fact that they didn't like the movie or have something against it. The fact of the matter is that the flash was not all that bad and doesn't deserve the low scores it is getting. I myself was not that big a fan of the movie because I found it very slow and very few funny moments.