I remember, when I was very young in the 1960s, reading an already-tattered book called (I think) "C-for-Charlie". The plot was about a boy who discovered a Gremlin -- C-for-Charlie -- who used to fly on aircraft in the war, but was now out-of-work. C-for-Charlie offered the boy three wishes, but the boy, being smart, wished for an unlimited number of wishes. C-for-Charlie is outraged, and negotiated down to one wish per day. That's when the mayhem ensues!
I'm certain I remember reading the book, but I can find no sign of it now. Does this sound familiar to anyone?