The cereal makes its first appearance in Pre-Hibernation Week, when a fish holds up a box of Kelp-O, suggesting that many other people eat it. In Shanghaied, the box has "one of eight essential prizes inside!", though SpongeBob does not get his prize. The cereal makes its most major appearance in Waiting, when SpongeBob sends in 99 box tops of Kelp-O to win a Free Toy. It also appears when Fred eats his candy coral (candy corn parody) in "My Leg!" and in the box can send a portal to Randomland
 Boxing and Taste
The taste of Kelp-O is very Kelpy, but it is known that SpongeBob likes it. The box has a plain yellow background with the words "Kelpo" written on top with a picture of a smiling kelp leaf below it.
- It is the first brand of cereal featured in the series. The second is Bran Flakes.
- Despite the fact that the cereal's name is "Kelp-O", the box reads "Kelpo", removing the dash and making the letter O lowercase. SpongeBob also writes "Kelpo" on his grocery list in That's No Lady.
- In the videogame, Battle For Bikini Bottom, there is a billboard for Kelp-O on the rooftop of a building.
- Randomland can be seen inside the box's candy corals