Utter crap.
This movie was one of the least funny sprite comedies I have ever seen. I don't get how anything here is remotely funny.
You have a silly letter from bowser that is a half assed excuse to start the "plot". Then Mario shows up to this location and some random monster is dragged off instead of Mario with out explanation of what it was or why it was taken. There is also no reasoning for why he attempts to help the goombas defeat Mario. Although I did somewhat like that battle sequence, I thought the whole Metal Slug tank was a lazy way to do a fight.
After the initial run in with the goombas, Mario starts running around randomly in a very stiff fashion. This is just filler to an already too long movie. What was worse was the "Fake LOL" castle. This was a poor attempt at random humor(my favorite kind of humor) because of the timing. You see from the start that the flag says "Fake LOL" and yet the camera still takes its dear sweet time to focus on that fact.
The subway I thought was terible. There were no funny jokes, and was the worse use of a Arnold Schwarzenegger sound board ever. It was just more mundain crap that I had to sit through. I did think that the Doctor Mario song was cool for about the first 30 seconds, but then it ended up like every thing else. And it's a shame when one small gem is hidden away like that. With the path this movie took, it could have been worked in anywhere and made sense(as much sense as any thing else did that is.)
In the end, I think this was a terrible movie and several minutes of my life I will never get back. How this made it to the top five and my inbox I will never know. If you ever make another movie of this quality again, it shall be too soon.