* Prototype is a game developed by Radical Entertainment and published by Activision. It's a superhero action-adventure game where you play as a character with shapeshifting abilities.
* Assassin's Creed is a game series by Ubisoft, focusing on historical fiction and stealth gameplay.
The two franchises are completely different and have no official cross-promotion or crossover content.
It's possible that some fans might have created custom skins or mods for Prototype that feature Assassin's Creed elements, but these would be unofficial and not sanctioned by either game's developers.