To good to be true? Well here it is. In 2009, a person with the username 'Hailrazer' made a portable version of that adorable little cube shaped Nintendo game console which he called the NCube. It was a 90 hour project. It even has a memory card slot for saving your progress in games. The over all design in my opinion resembles a Dreamcast. You can see the specs and details of the build here.
Fast forward to 2011. A man named Jonathan Shine has made a portable GameCube of his own, it derives power from an external power source which defeats the purpose of portablility but hey, something as awesome as the GameCube in the palm of your hands without slowdown? That is still very impressive.
Called the Ccube (Compact Cube), the case is made out of a cheap answering machine, plastic cement and many coats o paint. It was supposed to be a 2 week project but ended up taking 15 months to complete.
These are in no way practical but seeing bizarre mods by people around the world is one of the reasons why I love the internet.