The kelp fries look like normal fries that are thin. However, they somewhat resemble seaweed with the way they are shaped. They have had different appearances over the years. They are like French fries but in a Krusty Krab manner. Plus, they are likely made out of kelp.
Role in series
The kelp fries debut in this episode. SpongeBob makes them as part of a combo meal.
On some episodes, the quantity of Kelp Fries varies. An example of that is in the episode "Greasy Buffons" shown that the fries are 7 (or 8) in quantity while the episode "Kracked Krabs" has approximately 40+ fries on the platter. (However, these may just mean that the fries come in different sizes, the small box being a single serving while the large platter is made for a group serving.)
The boxes they are served in resemble those of McDonald's French fries since they are both red and contain the restaurant's logo initials in yellow letters on them.