Used Napkin is an inaminate object which only appears in the episode I Had an Accident. It is a napkin which has presumably
SpongeBob holding it.
been used, judging by its name. SpongeBob personified it after going insane from being isolated in his house following the event of him injuring himself. At one point, SpongeBob scolded the napkin by saying, "That's enough with the name-calling, Used Napkin!" Used Napkin is one of three "friends" SpongeBob made after deciding to live inside. The others were Penny and Chip.