There's a Lego fan out there named Akiyuki and he's created a gift for the world: a 100-foot long machine made from Legos that moves 500 hundred little balls around through various mechanisms. It's one of those things that once you see it start, you stick with it just to see what the balls are going to do next.
This machine took Akiyuki some 600 hours to finish, and it's safe to say he's probably earned the equivalent of a PhD in building Lego contraptions by this point. A visit to his site yielded some sage advice (with the help of Google Translate): "If you are making a Lego robot, accuracy is required…even a small angle of deviation in the base, in the rotary joint, it would be a big shift [and] absolutely tip."
He also offers a personal opinion of his work: "Cool."
That seems like a pretty good note to end on.