This totally awesome photoset comes courtesy of imgur user cthulhuandcats.
1. Get a turtleneck (duh).
2. Put it on like this.
3. Take the sleeves like so.
4. And pull them back.
5. Cross them.
6. Pull them back around ending with an "X shape" on the front and the back.
7. Then you tie them.
8. And cross the sleeves a second time.
9. Pull tightly to make into a double-knot.
10. Now, to get rid of the dangling sleeves, starting rolling the cuff end of the sleeve.
11. Keeping rolling.
12. Roll that bad boy until it looks like a rose.
13. And now you do the other one.
14. And then lastly, ake your fine self out looking stylish as heck without anyone know that you're actually wearing a boy's turtleneck.
Here's a side view and a view of the back for reference.
Oh, and fair warning: It doesn't work super well for all body types...
And, uh, horsemask is, of course, optional.
15. UPDATE: it appears as though a man has actually been able to pull this complex look off.
