Luna-P is a device used by Chibiusa (later Sailor Chibi Moon) in both the manga and anime of Sailor Moon. Luna-P is a hovering ball shaped like a cat's head with an antenna sticking out the top, and bearing a strong resemblance to another character in the series, Chibiusa's talking cat advisor Luna.
Upon the utterance of the vocal command "Luna-P Henge," Luna-P turns into all manner of objects and devices useful to Chibausa, such as a magic hypnotizing parasol or a sleeping potion.
Luna-P is also used by Chibausa as a means to communicate with Sailor Pluto and the other Senshi.
Later in the series when Chibausa transforms into Black Lady, she considers Luna-P to be her only true friend (anime), or tosses it away, calling it a stupid toy (manga).