Stop motion tetris is made out of people! Some people got together and played the part of the squares in the game of Tetris; a lecture hall with seats in a grid was the background.
What surprised me is how, at least in this particular game of Tetris, each individual piece got broken up pretty quickly, with only one or two pieces out of the original four remaining on the board. (The four people who made up each dropping piece were wearing the same color T-shirt, and there were enough different colors that for the most part one could assume that people wearing the same color and next to each other were part of the same piece.) This isn't obvious if you're used to, say, the NES version of Tetris (which is the one I played the most); the color scheme is different there. If you stop to think about it for a moment, though, it makes perfect sense that this should happen; it's very rare that four squares which fall at the same time all get eliminated at the same time.
Incidentally, the people writing that post say "Now, we're not mathologists". What is a mathologist? I would argue that mathologists are to mathematicians as musicologists (i. e. people who study music in a scholarly fashion, as opposed to those who produce it) are to musicians. However, there don't seem to be many mathologists in this sense; it's quite difficult to get the sort of deep appreciation for mathematics that one needs without actually doing mathematics, or so it seems to me.
By the way, Tetris is also a traditional Russian board game involving vodka. (Not really. And the amounts of vodka that this description invokes would kill even a Russian.)