This is for my 5 year old son. I shouldn't have shown him the picture 'cause he got on my case about this for 2 weeks. I finally obliged. Now my other son is asking for a regular green koopa troopa. Aaah, a parent's work is never done.
He's a fun little thing. Far from a perfect model as the design has some flaws but that shouldn't stop anyone from building it.
I used the PDO file from nintendopapercraft.com [link]
Click the Mario button on the right side of the screen. I recommend using the PDO so you can see how it's constructed.