It was a regular patty, but until Mr. Krabs stole a growth serum from Sandy and administered it to the patty, it started to grow.
It looks just like a normal Krabby Patty, only it is much bigger than other Krabby Patties.
Role in series
During its growth, it ate the Krusty Krab, and Cashy. It grew so large, it covered up, and ate most of the citizens of Bikini Bottom. It was finally destroyed after SpongeBob absorbed it into his body, making it 'spit out' everything and everyone it had 'eaten.'