- "Sonic? Sonic! This is not good! Eggman and his Empire has started a raid trip to locate the Chaos Emeralds to dominate the universe! I can't let this happen! Please, Sonic! You can trust me! I can help you!"
- —Sheen pretending to aid Sonic to stop Eggman.
Sheen the Monkey is a citizen in Sonic the Hedgehog: Speed Chronicles. He is notable for being aware of Dr. Eggman's wrongdoings and aids Sonic and his friends to find a secret place to stop him. However, after he is revealed to be a spy sent by Eggman to take down the Sonic Saviors, he becomes one of the primary antagonists in the series, while pretending to aid Sonic and his friends to "stop" Eggman in order to trap them, and aids Shadow and Rouge to steal valuable treasure for Eggman to fulfil his plans to dominate the universe.
Sheen is an orange monkey with green eyes and a long tail with a bandage on it. He wears white gloves, green and purple sneakers and a communicator which allows him to communicate with Eggman on the progress of his work.
Whenever Sonic nor his friends are around him, Sheen has pretended to be a worrywart that is aware of Eggman's wrongdoings, but he is too scared to stand up against the evil dictator by himself, so he needs someone to stand up against Eggman for him. However, when the truth about him has been revealed, Sheen reveals that he has been working for Dr. Eggman to take down the Sonic Saviors and has since then became one of the bitter enemies of Sonic. Ever since then, Sheen has started setting traps and spying on Sonic and his friends to report it to Eggman.
Sheen is also shown to be a coward. He, like all of Eggman's minions, fears Eggman's anger and wrath. He is constantly the victim of Eggman's violent abuse, especially when Eggman has threatened to give "flying lessons" to him whenever he has failed the latter or he failed to eliminate Sonic and his friends. Despite his fear of his boss, Sheen is still willing to work for Eggman to fulfil his plans.
Sheen is first seen in Episode 22, where is suddenly appeared in front of Sonic and his friends, and quickly told them about the bad news that Eggman has started a raid trip to locate the Chaos Emeralds for his plans to dominate the world. While aiding the four main characters, Sheen has unlocked a lot of secret doors where Eggman has kept his secrets in. Before Sonic and his friends could destroy Eggman's secrets, Sheen betrays the group by setting a trap on them, revealing to them that he is a spy sent by Eggman to take down the Sonic Saviors, and has stolen an empowered jewel from them to hand it over to Eggman. Fortunately, Sonic is able to break free from Sheen's trap and defeats the monkey with his Tornado Spin, forcing the monkey to retreat and get punished by Eggman by hanging him on top of a pot of boiling water.