Wow! Soup is pure grease in the form of soup, albeit served on a plate rather than in a bowl. It appears to have been suggested by Mr. Krabs because Plankton also had a food made entirely out of grease called Crispity Crunchities.
Due to containing nothing but grease, it is shown to give health problems to its consumers, yet cause them to crave it more even in the state of being sick.
Role in episode
Wow! Soup is served 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 due to its unhealthiness, despite still wanting to eat more.
Upon witnessing Patrick get sick from eating the soup, SpongeBob loses it and calls the health inspector to visit the Krusty Krab to take action against the toxic side effects of the grease products.