Multiples: How to tell twins from triplets

In Mary-Kate and Ashley Olsen, we have a good example of fraternal twins who are different from each other in significant ways - which,  if we look carefully, may betray their pre-birth origins as a set of multiple embryos. They were so similar as very young children that they were able to play the same role interchangeably in Full House.

The directors and producers of Full House did not want people to know that Michelle was played by a set of twins, so the girls were credited as Mary-Kate Ashley Olsen for most of the show's run. It wasn't until the final season that they were credited Mary-Kate and Ashley Olsen. Despite the fact that the Olsens are fraternal twins, their physical appearances were nonetheless similar enough so that few could tell the difference between the two.....

This from Squidoo:

Many of these things listed below were used to tell them apart when they were younger. Some can still be used now to tell them apart.

• Mary-Kate is left-handed. Ashley is right-handed.
•  Ashley is a little bit taller than Mary-Kate.
•  Ashely has a freckle above her lip

 And here is the crucial information:

• Mary-Kate is into sports and Ashley is more of a girly-girl. Mary-Kate usually dressed in sporty clothes, and Ashley dressed in skirts and dresses.

So Mary-Kate, left handed and born as the second, Beta twin with a double name, is probably the survivor of a monozygotic pair.  Meanwhile her sister Ashley, born first with a single name and right-handed, was probably a single embryo. But where did that male energy in Mary-Kate come from?  Why did she develop anorexia?  If there was another male embryo attached to the placenta that Mary Kate shared with her MZ mirror twin,  then there would be that little bit of male energy that sends her into male clothes...... also a sense that Someone Important starved to death as a result of her survival, not to mention her own MZ twin.  (The classic fetal assumption that seems to underly anorexia - but that is for another day.)