Sonic Heroes/Other characters

Froggy
Big's "polliwog pal" who lives with him in the Mystic Ruins. Froggy has been kidnapped by Metal Sonic, along with Chocola Chao. Metal Sonic copies Chaos' data from him.

Chocola
Chocola is a brown Chao and Cheese's brother. Chocola was kidnapped along with Froggy, by Metal Sonic. Metal Sonic copies Chaos' data from him.

Chaos
A mysterious liquid lifeform who protects the Chao from harm. He is not shown in the game, but does have a role to play in the game, as Metal Sonic kidnaps Froggy and Chocola and copies Chaos' data from them, as they have both encountered Chaos. Chaos' power allows Metal Sonic to melt into a weird liquid.

Chao
Cute creatures who can be bred and trained by you in Sonic Adventure and Sonic Adventure 2. They appear in some of the levels with Team Chaotix, as well as some bonus stages.