Cat naps. I have to remember how bad they are for you. Over the course of several days, the mind starts to break down worse than just sleep deprivation would cause. It's harmful over a long stretch to keep prematurely pulling the mind from NREM states without letting it finish cycling.
A few days ago a dialog with my brother opened up the query: "Is this why cats are so playful and odd?" if they never reach full REM they never are fully rested.
I've never seen that question arise in scientific study, although at the time of said discussion we were watching a nova documentary on dreams. They learned how to switch off sleep paralisys in animals, they showed dogs, cats and rats, up moving around but still asleep. I noticed the cats were the most agile. Just interesting.