You unlock Caddies by defeating the Pangya Festa with certain characters. (Except for Pipin) You must purchase them from the shop first just like the players. Outfits for the Caddies will be unlocked and available for purchase when you unlock the Caddies as well.

Brie Beat Arin's first Pangya Festa

Dolfini Complete the first Pangya Storyline with Kooh

Lola Complete the first Pangya Storyline with Uncle Bob

Pipin Complete the Tutorial

Quma Complete the first Pangya Storyline with Hana

Tiki Complete the first Pangya Storyline with Max
TitanBoo Beat Cecilia in Arin's first Pangya Festa

To unlock a new character, beat Pangya Festa with another character. This means the first storyline of Pangya Festa, unless otherwise mentioned.

Arin Beat Pangya Festa with Kooh

Cecilia Beat Pangya Festa with Hana or Uncle Bob

Kaz Beat Arin's final storyline. To access this storyline, beat the first storyline with everyone but Kaz, and wear Arin's Magic School Uniform.
Kooh Beat Pangya Festa with Max

Max Beat Pangya Festa with Cecilia

Uncle Bob Beat Pangya Festa with Scout