Well, in case anybody was absent for the whole Sonic Unleashed thing, that werewolf hand in the teaser trailer is Sonic. During the day, Sonic is the same old blue hedgehog, but during the night, Sonic turns into a werehog with claws and fangs. Yes, there is a day and night system in Sonic Unleashed.
When he is in his werehog state, he can swing around levels faster, move past obstacles quicker and hurl enemies as he chooses. Now, we also have the plot of the game.
The game begins with Super Sonic amidst a battle with Dr. Eggman and his robots. Somehow Dr. Eggman lures Super Sonic into a trap and using his latest invention misuses the power of the Chaos Emeralds to defeat Super Sonic and change something in Sonic's body. Dr Eggman appears to break the planet apart soon afterwards.[Sonic Unleashed's Big Secret Revealed!]
Having been broken apart by the evil Dr. Eggman, it's up to Sonic to put the pieces of the world back together again by retrieving the power of the Chaos Emeralds! In doing so, Sonic will find himself in a race against time and faced with an unusual situation that will challenge him in ways never before seen. Both day and night play different, yet important, roles in Sonic's newest quest... as the sun sets, a new adventure awakens. By completing a wide variety of action-packed stages, spanning the seven broken continents of the world, gamers will need to unleash Sonic's amazing abilities to save the world, and himself!