Mega Mario

Mega Mario is a form of Mario (and Luigi) that he can become by eating a Mega Mushroom in New Super Mario Bros.. This form allows Mario to greatly increase in size, allowing him to defeat every enemy in his path and break almost anything (including Flagpoles). The Mega Mario form is very useful sometimes, and the more things Mega Mario breaks, the higher the bar above his head will rise. If done right, Mega Mario can gain up to five 1-Up Mushrooms. Mega Mario also has the ablility to squash any of New Super Mario Bros' bosses in one hit, including Bowser in any of his forms.

In Super Paper Mario, when Mario (or Luigi, Princess Peach, or Bowser) grabs a Mega Star, he will turn 8-bit, much like his sprite from Super Mario Bros) and grow to giant proportions as well. As Mega Mario, Mario will be able to break blocks, enemies and anything in his path, much like the Mega Form from New Super Mario Bros.

Trivia

 * The "Mega" version of a character (though not named as such) actually first appeared in Paper Mario: The Thousand-Year Door when Bowser got a piece of meat while already Super Bowser. Additionally, characters' Super forms in Super Mario 64 DS are highly similar to Mega forms.
 * According to The InterNed, the music in Super Paper Mario that plays while Mario or another character (including a Koopa) is in Mega form is titled "An Unrivaled Battle."