Building on top of UT2D, an Unreal Tournament 3 mod that transforms the first-person shooter into a 2D shooter, Rikhan_z injected Epic's 2007 game with advanced blast processing technology.

In the process, he replaced its dreary environment with blue sky textures modeled after Sonic the Hedgehog's Green Hill Zone, as follows:

I'm sure that given the choice, most would have picked this method of introducing firearms to the Sonic franchise, rather than suffering Shadow the Hedgehog. To maximize your enjoyment of this clip, make sure to play the original Green Hill Zone music in the background, which you can load up with this convenient link.

And to see the reverse -- Sonic running around in Unreal Tournament 2004 (and riddling Mario and Futurama characters with bullets) -- there's a video for that, too!

[Via TechEBlog]