Ankle is Tingle's younger brother, and the son of the Pictograph Contest Manager. In the Wind Waker, he is being forced to push a block which rotates Tingle Island. In the Minish Cap, he is in Lon Lon Ranch and will fuse kinstones with you.
In Wind Waker, he tries to convince you to use the Tingle Tuner, an item that allows the second player to be Tingle. He tells you that when you do, Tingle is nice to him. "Oh so nice!"
Check out the Tingle Theory for more info.