'There Was a Little Cat'

There was a fluffy cat,
Who was a little fat,
With white in the middle of his forehead.
When he was good,
He was very good indeed,
But when he was bad he was horrid.

-- Adapted from Henry Wadsworth Longfellow

This morning I went to clean the litter box and the room smelled a little worse than normal. Then I discovered one of the cats had peed on a white plastic bag in the corner protecting the spare litter.

While I can't be sure who did it, I have my suspicions.