A modder, by the name of Evil Nod has put a Nintendo 64 into a Game Gear skeleton. Not only did he get the N64 in there, he also got the controller. So it has full reworking controller and a N64 crammed in there. What else could he shove in? How about a ram expansion pak? Yeah, he put one of those in there too.
Now, can someone do the same thing, with a Dreamcast? That would rock.