It looks like a regular Krabby Patty, except that it is gigantic in size. The amount of meat in the patty is so huge that normal size spatulas cannot flip it. It also appears to be too large to fit in somebody's mouth.
Role in episode
Squidward says that nobody has ordered a monster Krabby Patty in ages after a customer decides to order one. When SpongeBob tries to flip the patty, his spatula is broken in half and is taken to the hospital.
When Spat is fixed, another customer orders a monster Krabby Patty but Spat does not break this time. Instead, SpongeBob's arms break off.