puer aeternus - POO-air aye-TAIR-nus - a child (literally, boy) forever
Example: "Michael Jackson was considered by an analyst, in trying to explain the singer's strange actions, to be a puer aeternus."
As a starter: and as a former teacher in English, I hope to add to reader's vocabulary by presenting a word a day in simple terms that anyone can understand - from current use in publications, radio,TV, etc. Remember: use a new word three times in a day and it's yours forever!