Wow! Soup is pure grease that is served on a paper plate. It is also shown leaking off the plate, but not dripping off of it. It appears to have been suggested by Mr. Krabs because Plankton also had a food made entirely out of grease called Crispity Crunchities.
Role in episode
It is sold at the Krusty Krab before all the grease items are discontinued. When the customers try the Wow! Soup, they like it, but later become sick from it due to its unhealthiness, despite still wanting to eat more.
SpongeBob witnessing his best friend, Patrick, get sick from eating it is the last straw, and it results in the former calling the health inspector to inspect the Krusty Krab as a result of the side effects from the grease.