Small Bob

Small Bob is a saber-tooth tiger baby. He was found by Bob who named him so. He fought with Bob against Tartarus.

The Titans Curse
Atlas instructs mortals he hired to bring him dinosaur teeth to grow skeleton warriors with. However, they make a mistake and instead bring him saber-tooth tiger teeth. When watered, a baby saber-tooth tiger is grown.

House of Hades
Annabeth, Bob and Percy find a small cat when walking through Tartarus. Percy remarks that it was one of the saber-tooth babies, Bob names him Small Bob and takes him along with them.

When they reach the Doors of Death, Small Bob grows into an adult and defends Bob when he is fighting Tartarus. He also protects him when Bob is holding the button to send Percy and Annabeth to the surface.