The Moon is a celestial body that occupies the Imaginary Skies in Problem Sleuth. For a while, the Captain Snoop Bust and its noble steed were caught in the Moon's orbit, while the Moon was orbiting the largest Impetus Comb.
The Moon is not put to use until Pickle Inspector shoots it with the Sextant. The huge chunk taken out of the moon caused it to slowly descend onto BHMK's hat. It gave the final push to shoot Mobster Kingpin out of the Gravity Brassier and out Mount Saint Lardass.