The are various Bikini Bottomites that resemble a combination between their non-infected selves and a Krabby Patty. All of them resemble a Krabby Patty with lettuce and pickles. However, each one has traits or clothing shared with their normal selves.
While two hipsters were dining in the Krusty Krab, they said they want something different from the normal menu. Mr. Krabs took SpongeBob to his secret lab under the Krusty Krab, where Sandy created the new Secret. Mr. Krabs served it and, after a while, ate it, which caused him to turn into the first Krabby Patty creature.
When all the people in the Krusty Krab who ate the Secret Patty turn into Krabby Patty creature, they all left the Krusty Krab and caused havoc in Bikini Bottom, transforming many non-infected citizens into Krabby Patty creatures by feeding themselves to the citizens. They eventually destroyed the most of Bikini Bottom, turning it into a burning mess, and manage to transform everyone except SpongeBob and Plankton into Krabby Patty creatures.
The creatures then followed SpongeBob into the Chum Bucket where they infected Plankton and Karen. SpongeBob climbed onto some nearby bags of chum using sporks, breaking a bag and causing pre-cooked chum to fall out. One creature, who is actually Patrick, ate the chum, making him throw up the Secret Patty and turning him back to normal. However, he ate the Secret Patty again and became a Krabby Patty Zombie once more.
SpongeBob started to the throw chum into the creatures' mouths, which caused them to throw up the Secret Patties and turned them back to normal.
As everybody celebrated and left the Chum Bucket, Patrick, who was revealed to still is a Krabby Patty monster, or ate the patty again, offered a part of himself to the viewer before the episode ends.