Back in 2012, modder Modgyver wanted to do an Xbox 360 case mod, but was only interested in making something other than cutting a plexiglass hole on the side of the Xbox 360 case, which was a neat aesthetic but all too prevalent at the time. Instead, Modgyver put his Xbox 360 Halo Edition inside an original Xbox case.
The original Xbox was (thankfully in this instance) quite beastly, so Modgyver was able to fit all the 360 parts inside the original xbox case, including an internal power supply, hard drive and, for those worried about RROD, an additional fan coupled with the original case fan to prevent overheating.
Part of the back bezel from the 360 was reused to keep all of the audio, video, and USB ports in place and accessible just as they looked on the 360 model. Since the power supply was able to fit internally inside the case, the power supply jack from the original Xbox was also reused to keep the stock look.
The power and eject buttons function as they should, and the front USB ports were wired up to the controller ports on the front so the breakaway cables from original Xbox can be swapped to a wired 360 controller for the full original Xbox experience. The wireless controllers are still an option of course.