Riddle: Such a slim little stripe in a shiny, round coat! How it grows in the warm sun's bright rays! But its jacket still fits, and it's worthy of note That it isn't so, tall on cool days. Hint: It's not a fishing pole.
Riddle: I am round, I am sharp, I am small, I am big, I exist, then I don't. What am I?
Answer: The Moon. It's round when it's full, it's sharp when it's a crescent, its size can vary depending upon its phase, and it's gone when it's a new moon.