Nicknames that are fun are fine and quite cute sometimes. Friends of mine (childhood ones) whose nicknames I can remember were Pearl (Shirley), Pen (Wendy), Piece (Keith), Spoon (June), Babs (Barbara), Dave the Rave the Gangster of Love (Dave - he actually nicknamed himself that lol) and Baba (another Barbara).
Both of my GDs were given nicknames by their parents: Boz (the eldest) and Chunky (the youngest, yes, she was a bit large as an infant but now as thin as a reed) and both hated those nicknames. The youngest now verges on anorexia as she is obsessed with keeping her weight down.
There was an item on the news this morning about depression and especially depression affecting young people; turns out that most of begins before their 15th birthday - maybe nicknames aren't as harmless as we think (not that I'm implying they are the only reason for depression).