It is the third Sonic Rivals Game.
Eggman Nega goes mad with power and turns mobians into cards! But this time the cards transport them to Nega's New Machine, The Robotcizer!
- Sonic the Hedgehog: The World's Fastest Hedgehog, Sonic works with Tails to investigate the Chao disappearances.
Sonic's Signature Move is "Sonic Boom". This allows him to break the sound barrier in an instant and take off at high speeds. This move also destroys enemies and damages other opponents.
- Miles "Tails" Prower: Sonic's Friendly Sidekick, Tails assists in finding the missing Chao.
Tails's Signature Move is "Tail Copter". He can quickly cover short distances and large gaps by flying.
- Knuckles the Echidna: The Guardian of the Master Emerald, Knuckles teams up with Rouge to find it once it goes missing.
Knuckles's Signature Move is his "Knuckle Slam". Knuckles punches the air and surrounds himself with a fiery forcefield.
- Rouge the Bat: A Government Spy with a great desire for jewels, Rouge teams up with Knuckles to find the Master Emerald.
Rouge's Signature Move is "Bat Guard". A swarm of bats circle her and act as a damaging shield to other players. She can also launch the bats one by one to attack enemies and players.
- Shadow the Hedgehog: The "Ultimate Life Form", Shadow works with Metal Sonic to stop Eggman Nega's plans.
Shadow's Signature Move is "Chaos Control". This slows down the other player's movement for a few seconds.
- Metal Sonic: Sonic's Robot doppleganger, Metal Sonic is sent by Eggman to work with Shadow.
Metal Sonic's Signature Move is "Copycat". This allows him to copy the Signature Move of the other player. In the event that Metal Sonic is playing against Metal Sonic 3.0, or there is no opponent, Metal Sonic's Signature Move defaults to "Sonic Boom".
- Silver the Hedgehog: A Psychokinetic Hedgehog from the future, Silver works with Espio to rescue the missing Chao.
Silver's Signature Move is "ESP". He temporarily alters the other player's controls (Often causing them to go backwards or look around).
- Espio the Chameleon: A Ninja Detective, Espio works with Silver to solve the case of the missing Chao.
Espio's Signature Move is "Chroma-Cammo". He cannot be seen by enemies or other players, and gains a speed boost.
- Big the Cat: A gigantic cat with a pet frog. Big works together with Omega to find Froggy.
Big's Signature Move is "Fishing Pole Tornado" He swings his fishing pole in circles and creates a tornado.
- E-123 Omega: A robot built by Eggman, but now serves Shadow. Omega works with Big to find Froggy.
Omega's Signature Move is "Machine Gun" he shoots projectiles out of his arms.
- Dr. Eggman: The Main antagonist of series, who actually plays a protagonaistic role in this game. Eggman Nega disguises himself as Eggman to fool the eight playable characters, however, the real Eggman is giving instructions to Shadow and Metal Sonic and gives them missions they must complete, only 4 characters can tell its Eggman Nega (Shadow, Metal sonic , Sliver and Espio )
- Eggman Nega: The Main antagonist of the game. The player must battle him at the end of each zone, however he is disguised as Dr. Eggman. During the storyline he hires Rouge to find the Chaos Emeralds for him and creates Metal Sonic 3.0, an upgraded version of Metal Sonic.
- The Ifrit: A giant fire like beast unleashed by Eggman Nega. He attacks the player who must fight it and another character who is under his control.
- Metal Sonic 3.0: An upgraded version of Metal Sonic. He is created by Eggman Nega and helps him to release the Ifrit at the End of the game. The player must fight him during Metal Sonic's story. The player can also unlock him as a costume by copying every playable rival's signature move.
- Amy Rose: Sonic's Self-proclaimed girlfriend, she is kidnapped by Nega.
- Tails Doll: A insanely creepy doll, he stays near Eggman during the story.