C
Chao - a playful creature introduced in Sonic Adventure
Chao Garden - an area where Chao live and play
Chao Karate - a feature in Sonic Adventure 2 Battle where Chao fight until one cries and loses its stamina
Chao Kindergarten - school for Chao where they learn different abilities in
music, art, dancing, and other physical activities
Chao Walker - a machine built by Tails for Chao to fight in Sonic Adventure 2 Battle
Chaos - an enemy that first appeared in Sonic Adventure,
a protector of Chao, and becomes more powerful with each Chaos Emerald he absorbs until he becomes Perfect Chaos
Chaos Control - a technique first introduced in Sonic Adventure 2/Sonic Adventure 2 Battle that allows Sonic the Hedgehog and Shadow the Hedgehog to cross great distances
and even freeze time
Chaos Drive - a power source inside GUN robots that can be fed to Chao (which raises their statistics) in Sonic Adventure 2/Sonic Adventure 2 Battle
Chaos Emerald - an emerald with special powers
Charmy Bee - a character that first appeared in Knuckles' Chaotix and later appeared in Archie Comics Knuckles the Echidna series
Cheese - a Chao that always wears a bowtie and follows Cream the Rabbit
Chili dog - Sonic the Hedgehog's favorite food
Chris Thorndyke - a little boy that saved Sonic the Hedgehog's life in the first
episode of Sonic X; Chris helps Sonic and his friends search for
the Chaos Emeralds
Cosmic Interstate - a system of roads that connect
similar universes together; found in Archie Comics Sonic the Hedgehog series
Cream the Rabbit - a polite, young girl who first
appeared in Sonic Advance 2; her best friend is Cheese
Cyclone - Tails's machine in Sonic Adventure 2/Sonic Adventure 2 Battle