Plankton hides inside of a ketchup bottle in an attempt to obtain Old Man Walker's Krabby Patty once squirted on it. However, due to Walker's poor eyesight, he squirts the bottle in the wrong direction, causing Plankton to go flying across the Krusty Krab.
An artist is seen squirting ketchup and mustard on a plate to create the Fiasco.
"Little Yellow Book"
Squidward has SpongeBob deliver a bag of ketchup to the dumpster in the back of the Krusty Krab, which Patrick is inside. Patrick then takes the ketchup out and remarks that it would be a good addition to an old diaper he found.
Ketchup, along with mustard, appears in Battle for Bikini Bottom at a condiment bar in the Krusty Krab. When SpongeBob is granted access to the restaurant, he is able to destroy various property of it, including the two condiments.
Ketchup appears in SpongeBob Moves In! as a cooking material made in the Krusty Krab. It requires two tomatoes to be made. It takes four seconds to make, gives 1 happiness when collected, and gives 8 coins when used.
Patrick likes to put ketchup on diapers, as seen in "Little Yellow Book."