Decided to finish up an old pose sketch, and the result was some simple cheerful art of Jack prancing around in his boxer shorts in a carefree manner.
The "why" is rarely clearly defined when I draw things like this, though.

Maybe he's ready to go swimming or jump around in a sprinkler, who needs swimwear when you already have boxers and you're a fuzzy hyena child? Perhaps he's burning off some energy before going to bed. Or maybe he's doing it on a dare...