Practically a Disney heroine- from the back cover of Excalibuer #4
Meggan's past remains shrouded in mystery. Her entire identity consists of what she is at the moment, and she defines herself by who she is with. She is a shapechanger who met Captain Britain years ago. At the time she looked fearsome and freakish, after having grown up close to people who declared her a monster- without knowing it, she shapeshifted to meet their expectations.
After meeting Captain Britain, she soon fell in love with him. When she discovered her powers and was able to manipulate them, she changed her appearance to what she probably assumed would please him. She was right- shortly thereafter their friendship changed to love and they have been together ever since.
Still, because of Meggan's upbringing, she is entirely dependant on Brian for her happiness. If he shows the least sign of anger towards her she will often fall apart. Because of this, when the team first started she gravitated towards Nightcrawler and began to lean on him for some support. He was obviously attracted to her, and for a time she seemed to be returning that attraction, though nothing ever happened between them. It eventually turned out that Meggan was an empath who sensed what people were feeling, and then reflected it in herself; since her shapeshifting was very linked to what she was feeling at any time, her appearance often changed as a result of the moods of those around her. Although her love for Brian is true, she can be easily swayed by someone else's strong feelings. She is naive and trusting, but a strong-willed woman in terms of goodness.
Meggan spent most of her life almost completely illiterate, and most of her time after meeting Captain Britain watching the telly. From the start of the series, she looked like a sex symbol but acted like an innocent little girl- this feature was one of her most endearing qualities. She, unlike most other people around her, can be truly happy without worry. She is one of the truest optimists the world has ever known.
During Davis's run, we never found out exactly who Meggan's parents were or what secrets her past held. We did find out that her true form was a tall, somewhat elfen-looking blonde female who was able to see the life energy of those around her. Although it was never explicitly stated in the series, as it turns out Meggan is a Faerie but is unaware of it. This was implied from the start, once you go back and look; in issue #11, Meggan is ill at ease in Fenborough, a place supposedly once populated by magic and fairies; in #12 she is welcomed by the fairies in the magical land Excalibur has traveled to. Prince William says that the fairies appear to be welcoming her home, as if she were a princess of their kind. And Meggan's true form makes it relatively obvious that she is far more than human. As far as I know, though, this heritage still has yet to be addressed in the book as it stands now.
By the end of the series, Meggan and Captain Britain were engaged to be married (finally!!). They went through a few rough spots but in all it looked promising for them.