When our identical twin sons were born, they had started to develop twin-to-twin syndrome. One (Jonathan) was a full pound heavier than the other, and considerably redder, due to getting most of the blood from the placenta, while the other one (David) was quite sallow due to lack of blood. David looked jaundiced, though he wasn't, while Jonathan looked like someone had given him a Betadyne bath. They also had easily distinguishable cries. Otherwise, they looked exactly alike, down to the folds in their ears.

About a week after we brought them home (they were maybe ten days old), we noticed that the red and yellow colors were fading, and we realized we'd better do something fast or we'd never know which was which. I painted Jonathan's fingernail red (since he'd been the red one), and we decided we'd always dress him in something red, too. We kept the nail polish until they were over a year old, and had enough hair to give them different haircuts. The haircuts lasted until about sixth grade, when they rebelled and insisted on growing their hair long. By that time, I had no problems telling them apart, although their teachers and peers sometimes did. But without the nail polish and haircuts, I know I would have been completely unable to distinguish them.