Because even 16-year-old girls have occasions for which their socks really ought to match, I also made my sister a pair of matching socks. Not quite so matching as to be identical twins, but these are at least the same yarn, in the same colorway, in the same pattern and the same size. And yes, the left sock is inside-out. That was on purpose, too.
Pattern: Hypnosis by Janel Laidman
Yarn: Colinette Jitterbug, in Lapis, about 240 yds used
Needles: 24" Addi turbos in US size 1.5
Size: to fit a woman's 8
I modified the pattern a little bit, to change how the pattern interacted with the heel, and I think I worked a different heel (I don't actually remember now). Jitterbug is a fun yarn (also a fun dance, by the way), although a little thicker/heavier than a lot of the sock yarns I use.