Blaze the Cat first appeared in Sonic Rush, and later Sonic Rush Adventure. Her speed rivals Sonic's except she uses fire as a source rather than speed alone.
Blaze is from another dimension and seems to play a similar role to Sonic. Sonic has Dr. Eggman, Blaze has Eggman Nega. Sonic has Chaos Emeralds, Blaze has Soul Emeralds. She can also harness the power of the Soul Emeralds to go into a Super Sonic-like state. She was also hinted to be the guardian of the Soul Emeralds, like Knuckles is the guardian of the Chaos Emeralds. She was also hinted to have feelings for Sonic.