Pearlie is a big pair of dentures that makes the wearer smile whether they like it or not. SpongeBob wore this in the episode "Picture Day."
Pearlie has white teeth and light pink gums, just as a person would see in regular dentures. It is very large.
Role in episode
When SpongeBob finally gets to Mrs. Puff's Boating School to get his picture taken, he is still dirty and is crying. The Photographer cleans him up by spraying water at him, but SpongeBob still continues to cry. Then the Photographer gives him clothes, then he puts a Pearlie in SpongeBob's mouth, and then they take the picture. Then SpongeBob receives his yearbook, it turns out that all of his classmates are wearing Pearlie also. SpongeBob comments "Hey! I don't look so bad after all!"