I’ll briefly try to explain how to turn your 3DS into a Mega Drive. First of all, all you need is a New Nintendo 3DS LL (Metallic Black) and a New Crystal Shell for New 3DS LL (Clear) go to http://firestorage.jp/download/1d0f36deeb0486b8e6f7e0603e88cc3dc8e9b4de and click the red text and type MD. A download link should appear for a Zip file containing a text file, PSD and a JPG (the latter pictured here). Print the image at 350dpi (width 17.42cm height 18.87cm) then cut in the black line (grey part is overlap) and then add to your cover and then your New Nintendo 3DS LL and voila – your 3DS LL is now a Sega Mega Drive! All credit goes to @Shigatake