This Mario papercraft is a Boo (Boo Diddley or Boo Buddy), a recurring enemy in the Mario series, the paper model was created by aardonix. Boos are common ghost enemies in the Mario series that first appear in Super Mario Bros. 3. These include King Boo, Pink Boo, Boolossus, Bomb Boo and Big Boo.
They are a type of white spherical ghost with menacing and constantly open mouths. They are known for their large tongues and small "arms" of some sort. However, the most distinctive characteristic of the Boos is their shy personality, where they cover their faces when someone looks them directly at the face. They will uncover their faces once the subject turns around. Goombario's tattle for the Boo Igor in Paper Mario states: "He probably was a merchant before he became a Boo," implying that current Boos may have once been living beings. It is revealed in Super Mario Galaxy that they speak in Booish. [Source: Mariowiki]
You can download this mario paper craft model here: Super Mario Bros. 3 - Boo Free Papercraft Download