A Pretty Patty is a colored Krabby Patty that appears in the episode "Patty Hype" as well as the online game Which Krabby Patty Are You? They were extremely popular but had the unfortunate side effect of changing the color of the people who ate them to the color of the patty.
They look like normal Krabby Patties but are differently colored. They still have the same ingredients as the original Krabby Patties, however.
They are loved by all the Bikini Bottomites and the stand easily outsells the Krusty Krab, which has been seeing fewer customers for a while. However, before long the colored patties turn the customers' skin into an assortment of colors and even cause three citizens' tongues to change different colors. As a result, everyone hates them afterward and the episode ends with Mr. Krabs getting chased by an angry mob.
Pretty Patties are sold at a stand created by SpongeBob and Patrick. There is a stand to sell the patties, and right next to it is a stand that gives free money away to customers, much to the horror of Mr. Krabs.
The stand is later taken over by Mr. Krabs, and the Krusty Krab key is given to SpongeBob.
Soon afterward, the customers demand a refund after discovering that Pretty Patties turn them into the color of the Pretty Patty that they ate.
The first Pretty Patties customer was Incidental 40, who bought a purple patty, as purple was his favorite color.
The last Pretty Patties customer was Incidental 42, who got a glow-in-the-dark tongue following his consumption of the burgers.
If Pretty Patties used the same recipe - with exception of the food paint - for Krabby Patties, SpongeBob would owe Mr. Krabs royalties fees.
When SpongeBob reveals the Pretty Patties to Squidward and Mr. Krabs, he says "Available in six designer colors." However, they are seen in approximately 22 different colors.
Although, six designer colors of the Pretty Patty are shown on the art palette, which could not fit 22 in total given its small size.
These were the first Krabby Patties to be sold outside the Krusty Krab.