A Pretty Patty is a colored Krabby Patty that appears in the episode "Patty Hype" and 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 (or their tongues) 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.
They are loved by all Bikini Bottomites and the stand easily outsells the Krusty Krab, which was 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: one glow in the dark, one yellow, and one orange with green dots. Everyone hates them afterward.
The venue in which Pretty Patties are sold is 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 money away to customers. The stand is later taken over by Mr. Krabs, and the Krusty Krab key is given to SpongeBob.