WARNING: This contains SPOILERS for Sonic the Hedgehog 2.
Sonic the Hedgehog 2's post-credit scene not only introduces an important character from the games but also shifts the balance of power in the Sonic movie universe. As promised by the director, Sonic 2 delved into the world of Sonic and brought many elements from the games to the screen – much more than the first film did. Tails and Knuckles joined the franchise, and what was once a more realistic setting with Sonic as a part of it evolved into something closer to a video game world.
That said, Sonic 2 is still maintaining a certain sense of realism as set by the first film, including finding reasonable explanations for elements that the games usually overlooked. Most of the human characters from the first film also return, including James Marsden's Tom and Tika Sumpter's Maddie. However, adding a famous character from the video games was what truly helped Sonic 2 find its perfect hook for Sonic the Hedgehog 3.
Related: Why Jim Carrey Is Only Making Sonic Movies Now
In Sonic 2’s post-credit scenes, G.U.N soldiers are discussing the aftermath of the battle against Robotnik, and the possible death of the villain when one of them mentions the discovery of a file called Project Shadow. The file had been discovered when G.U.N was deleting all mention of the Robotnik name from the database. The scene then goes on to reveal a Sonic-like creature being held in some sort of capsule, waking up from what appears to have been a long sleep.
The black hedgehog at the end of Sonic 2 is Shadow, one of the most important characters in Sonic's mythology and a recurring character in several games and animations in the franchise. Shadow is essentially a rival of Sonic, though his
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