It is a bacteria-infected Krabby Patty that is very poisonous. It is covered with light green mold and hairs and contains tainted buns, meat, and cheese. Consumption of it will result in hallucination of a giant hamster named Cuddle Eat Hugs.
Role in episode
Squidward and SpongeBob are cleaning up the Krusty Krab. Squidward finds a moldy Krabby Patty and throws it away, but SpongeBob prevents him from doing so because it is still a Krabby Patty nonetheless and he thus thinks it should never be wasted. SpongeBob then takes a bite of the patty and becomes sick to his stomach. He runs to the back of the restaurant to vomit and the Aged Patty causes him to hallucinate a giant hamster named Cuddle Eat Hugs.
The next day, SpongeBob awakens to find Cuddle Eat Hugs gone. SpongeBob figures a Krabby Patty would make him feel better, so he takes another bite of the old patty, sickening him once more. At that moment, Cuddle Eat Hugs returns and he and SpongeBob reunite with a hug. Cuddle later reveals that no one can see him because they did not eat the aged patty. He then suggests that SpongeBob feed others the Aged Patty, so he does just that by cutting it into pieces and selling it at a stand in the Krusty Krab for free.
Everyone runs up and eats pieces of the aged patty, and just like SpongeBob, they hallucinate and see Cuddle. However, things take a turn for the worst, as Cuddle Eat Hugs begins to eat everyone (in reality, they are all having hallucinations caused by side effects of food poisoning from eating the old patty).
The next day, everyone, but SpongeBob, leave in anger and disgust from Cuddle’s actions. SpongeBob eats another piece of the aged patty to confront Cuddle for his actions. Cuddle explains that the “E” in his name stands for “Eat.” SpongeBob then gives Cuddle the last piece of the patty. Cuddle then hallucinates himself as a real life hamster in a child’s bedroom. He then says, “Oh, pellets,” as the episode comes to an end.
This is the second rotten Krabby Patty that SpongeBob has eaten in the series, the first being the rotten version of Patty in "To Love a Patty."
The only characters who do not eat the Aged Patty in the episode are Gary and Squidward.
The patty’s stench has the ability to make a knife melt.