It is also the name of the most annoying
monster in the game
Gauntlet 2. It appears as a little
spark zeroing in on the player. When It touches you It disappears and the game tells you "Red wizard is now It!" and all the other
monsters come running after you.
It's first appearance is on on of the earliest levels, and there's always a player close enough to be caught by It. From memory, when you are It a little spark circles your character - my memory is hazy due to having to slaughter millions of monsters while trying to tag someone else.
With one player this is not a big issue, as all the monsters come after you anyway, but when there's two or more people playing you get all the monsters and your friends get to laugh at you. The clever part is if you can tag someone. They become It, turning an ordinary computer game into a more destructive and bitter version of the playground game.
I call the It Monster annoying, but the game wouldn't have been as hilarious without him - I miss It.