I suppose the biggest surprise I got was when the supernumerary nipple under my right armpit turned into a miniature breast. Before HRT I didn't know it was a supernumerary nipple though, I just thought it was a skin blemish. It took until year four before it woke up and bloomed into a proper little type 1 supernumerary nipple. It's actually very cute, and no I won't show you a picture because you'll have to marry me first to see it and I'm very fussy about whom I would allow to be that close to me.
When it happened I thought something awful was going on like some kind of icky cyst or something and I was worried, but once I found out what it was I didn't mind in the slightest. My daughter has one too, but because it's away from the milk line her one just stayed being a tiny blemish.