The story of *Sonic the Hedgehog 2* begins relatively soon after what happened in the initial movie. Following his defeat, Doctor Robotnik—played by Jim Carrey—found himself exiled from our planet and experienced a rough landing on the Mushroom Planet with his spacecraft. He needs Sonic’s quill to get away; it's full of substantial power, and he employs it to transmit a call for help. This summons Knuckles, portrayed by Idris Elba, another creature that is both animal and humanoid, possessing extraordinary strength like Sonic himself. Knuckles represents the final surviving member of the echidna people, who were destroyed in a conflict which also resulted in Sonic's arrival on Earth many years prior.

Source on TMDB