Dudeeeeee, this hit my nostalgic years. Halo has been a big part of my life, almost as much as Sonic! Heck, I even own some of the guides and book manuals!
Aside from my nostalgic speaking, per-say, this animation was really well done! Outstanding and amazing! To also even imagine Sonic characters replacing the specific scene(one that I personally think is important to the entire Halo series), was outstanding, especially on the way you sorted the characters their roles.