It is a black haircomb that is rather bizarre in appearance; it contains three sides for one to brush their hair rather than one.
Role in episode
While locked out of his house from going outside to get the up-to-date newspaper, SpongeBob attempts to gain entrance by going through his bathroom's open window. During the process, he hears Larry going through his medicine and hopes he doesn't touch his special comb. While examining himself in the mirror, the former deems himself good enough to eat, but thinks he could use some teeth whitening, so he rummages through SpongeBob's medicine cabinet for toothpaste and then gets distracted by the bizarre nature of the latter's haircomb. After thinking that he has "aired it out a little," Larry closes the windows, causing SpongeBob to break his fingers and fall down.