Sagittarius

Sagittarius is the name of Olimars son, and also is a ship part in Pikmin 1. He is usually a green colored captain.

Pikmin the huge debt
Sagittarius is a playable character. Most of his creature notes involve something childlike and fun.

How to unlock him
It is easy to unlock him. All you have to do is go to Suma Dock on day 4 and talk to him. He says " Thanks for letting me come along dad! Im excited to find animals with you and Uncle Louie". And there you go he is then playable.