Stache

A mustache (also called moustache or 'Stache) is a form of facial hair common in male adults such as Mario, Luigi, Wario, and Waluigi. Mario (and thus the palette swap Luigi) was originally given his mustache to clarify the borders of his nose, while Wario and Waluigi's mustaches are just parodies of Mario and Luigi's and are therefore angular and unrealistic. Many other characters, like the Millenium Star imposter, Eldstar, one of the Delfino Police, and Toadsworth, also have mustaches. Additionally, mustaches can be a source of pride, as demonstrated by the various mustachioed bosses of Super Mario 64. In Super Mario 64 DS, they often insulted Mario, Luigi, and Wario for their supposedly inferior mustaches.

In the Mario & Luigi series, the mustache, under the name of  ' Stache, acts as a statistic in the game. It gives Mario, Luigi, Baby Mario and Baby Luigi better chances at getting a "Lucky" shot in battle, and gives discounts to items bought at shops. Bowser's equivalent in Mario & Luigi: Bowser's Inside Story is "Horn."

According to Fracktail in Super Paper Mario, Mario has a level 5 mustache.

Trivia

 * In Super Paper Mario, the "Yellow Apple" makes those who eat grow a mustache.