A little chojin that can change shape.
Puyo-Puyo is introduced during the 2nd Kaiju Extermination Arc, where he is recruited as part of a team whose purpose is to eradicate a group of space-bandits from attacking Planet Rakka. He can change shape and often acts in an integral role in helping his team, such as changing his shape to transport his team to the battlefield.
Beansman leads his group of Seigi Chojin to Africa, where he seeks to recruit another member to their team.  Kinnikuman teases Puyo-Puyo, once found, about how he trembles and his unusual appearance, and this triggers an argument between the two, which culminates in Puyo-Puyo transforming into a large fist and knocking out Kinnikuman. Puyo-Puyo then travels with them to Antarctica, where they recruit Crystalman. 
Once their team is fully assembled, Puyo-Puyo transforms into a type of roller-coaster, and transports them to Planet Rakka.  Puyo-Puyo is sent to guard the fortress with Terryman and Kinnikuman. They eventually flee the fortress when their enemy merges into one giant opponent, but - as a team - defeat them and save Planet Rakka. 
- Puyo-Puyo has no hobbies