This is Elizabeth Zimmermann's Baby Surprise Jacket:
Elizabeth Zimmermann is something of a legend in the knitting world. She wrote books in the 60s and 70s that approached knitting in a very relaxed, no-nonsense way, and she's regarded as kind of a mother of the craft as it's known today. I admit I haven't read much of her work, but I have heard about the Baby Surprise Jacket for some time, and have been determined to knit one.
I have to say, the thing is a marvel. Look at that picture above. It's a blob, right? You can't imagine how it's going to turn into a jacket, right? It's knit all in one piece; in fact, if you have a length of yarn long enough (I didn't), you could knit it all in one string--at no point do you need to cut and reattach the yarn; that in itself is cool. Not only that, even though you know it's not the case, you feel like you're knitting a big rectangle, and that both cuffs are knit on one side of the rectangle, and the buttonholes are on the other end, and you have no idea how the thing is going to rearrange itself. I consider myself fairly good with spatial visualization, but I have to admit, the jacket is well-named: the "surprise" is that it makes a jacket at all.
Voila! Here is the Baby Surprise Jacket, properly folded up:
There are only two seams on the thing, running from the neck to the cuff on top of each sleeve. There are no seams under the arms or at the sides. Furthermore, if you examine the thing, you'll find that the cast-on edge runs across the back and around each cuff, while the bind-off edge runs around the hem and up each front edge. This is cool because the cast-on edge is always stretchier, just the thing you'd want to have at the cuffs. I swear, after I finished the thing, I spent about twenty minutes just looking at it, marveling at the design.
Seriously, it's magic.