The lead! I wrote the role with Jaleel White's Sonic in mind (https://youtu.be/FRJohy5kN0Y) but I'm open to other interpretations, so have fun with it! Be warned that Sonic has a lot of lines, and that you'll need to swear, shout, kill God and love Mario. 

This version of Sonic starts out as you would expect, but through trials and tribulations spirals down into a confused, depressed and morally grey antihero. The first line comes at the beginning of the story, and should be Sonic as you expect him to sound. He's sarcastic, he's quipping, he's taunting Robotnik. The second is at the very end, when he's been ground down. It should have less of the affected enthusiasm that the first line has. And the third is him in Fleetway Sonic the Comic Super Sonic mode, when he turns evil. He's singing Don't Stop Me Now, but you don't have to be any good at singing. It's not a musical number, it's Sonic singing to himself dementedly. 

Also here's Don't Stop Me Now since people haven't been doing it to the tune: https://youtu.be/HgzGwKwLmgM