Napkin is scared of being in liquid. When he's in liquid, he is stained, and it takes him long to recover. For this reason, he almost never drinks.
Disregarding Eggy and Brownie, of course, Napkin is the youngest contestant, and sleeps the most often out of everyone. He's hardly ever energetic, but during eliminations, contests, etc., he stays awake and alert.
He died in BFS Ep. 22 and is temporarily revived in BFAS Ep. 6