Jack

Jack is the fastest Skelanimal there is! It is impossible to catch him once he's started running. When he was alive he would race against turtles (including Pudge) just to show off his speed.

Appearance
Jack has tall bunny ears that go into his oval-shaped head. His skull has two rabbit teeth at the bottom instead of the common rectangle shape most Skelanimals have. His heart is placed in his chest, between his arms.

How Jack Became a Skelanimal
Jack was racing a turtle, and ran so fast that he lost sight of his opponent. Jack turned around to check where the turtle was and accidentally ran straight into a tree, causing his death.

Passage from Skelanimals website
Jack was nimble, Jack was quick. He was so fast, it made you sick. Showing off his speed, he challenged a turtle. The race then started, he shot like a missile. As he ran so far, he turned around to see Where he left the turtle, and then hit a tree.

Trivia

 * Jack is the only Skelanimal to have this type of teeth.
 * His name is a pun on "jackrabbit", which is another name for a hare.
 * Jack is also based on the poem “Jack be nimble, Jack be quick, Jack jump over the candlestick.”