Well, the first time around, it happened because Loki was a brat and cut off my hair. As recompense, he brought me a wig of pure spun gold, and once I put it on, it began to grow as my own hair. For this lifetime, though, we had a power boost some time ago, and this was the souvenir I got to keep from that.

Well, perhaps I'll send a half dozen of each, then?