Mr. I

A Mr. I (also parsed Mr. I. or Mr I ), also known as Spinning Eye, is an enemy species in the Mario franchise, debuting in Super Mario 64. Its name is self-descriptive; they seem to be nothing more than a giant eyeball. Additionally, Mr. Is are usually completely immobile, as they can only rotate around in place. A larger, subspecies, Big Mr. I has also appeared in various titles.

Super Mario 64 / Super Mario 64 DS
They first appear in Super Mario 64, where the only thing they can do is shoot pink bubbles at Mario from their pupils. They always watch Mario when he is close, and can be dizzied into submission if Mario runs in a circle around them in either direction, rewarding Mario with a Blue Coin. The standard Mr. Is can be found in Big Boo's Haunt, Lethal Lava Land, and the Hazy Maze Cave. After being dizzy, it slightly shrinks before dying. The much larger version, Big Mr. I, is in the attic of Big Boo's Haunt.

In the remake, their pupils are now oval-shaped, and said pupils are now dark blue instead of black. Also, the bubbles were changed to balls of light that change color, but are primarily turquoise.

Mario Party 2
Mr. I appears in Mario Party 2 in the Horror Land board, where he offers to "warp" the player across the board for ten coins, though his "warping" actually involves him rolling and chasing the player (and any others along the route) to the other side of the board.

Mario Party 5
A Mr. I appears in Mario Party 5 as a weapon in Super Duel Mode. It shoots a blue laser to stun enemies.

Mario Party Advance
In Mario Party Advance, a notable Mr. I appears as a resident of the Horror Area; he is in love with Princess Peach.

Mario Party 8
In Mario Party 8, Mr. I and Big Mr. I appear in the minigame Eyebrawl, where instead of running around them like in the Eye Sore minigame from Mario Party 3, the player must draw circles around them with the Wii Remote. In this game, Mr. I's iris and pupil take on a more oblong shape. Whoever gets Mr. I dizzy first wins the minigame. The loser is haunted by Mr. I.

Mario Party Superstars
Mr. I reappears in Mario Party Superstars, retaining its design from Mario Party 8. Just like in Mario Party 2, it appears on Horror Land and will warp the player to the other side of the board. They also run the losers out after a game on Horror Land has ended.

Super Paper Mario
In Super Paper Mario, Mr. I, identified as Mister I, appears in Merlee's Mansion and Castle Bleck; these Mr. Is are immune to conventional attacks, and can only be defeated by running around them repeatedly while using Mario's Flip technique. Alternatively, the player may use Fleep's ability on them to defeat much easier. A total of three can be found in the game. In this appearance, Mr. Is attack the player by shooting them with a cyan laser beam, like in Mario Party 5. The game also introduces a sub-species of Mr. I is called Red I.

Mario Party Superstars
Encyclopedia bio: "Giant floating eyeballs. Run circles around them to stop them from seeing straight."

Trivia

 * In the files for the Super Mario Mash-up in Minecraft: Wii U Edition, there is a picture of an Ender Chest with a Mr. I on it. The concept for the Mr. I chests was scrapped before the final release, where they are Shy Guy-themed instead.