Incidental 42 is a red-orange fish with beige fins and light olive-green lips who wears a baby blue top. In Season 1 and in some early Season 2 episodes, he had oval shaped eyes, and visible gils on his head.
In "Neptune's Spatula," part of the audience who watch SpongeBob and King Neptune's cooking battle.
In "Dying for Pie," SpongeBob shows Squidward to Incidental 42 at the park. Squidward says "Hey Frank."
In "Patty Hype," Incidental 42 is a starving fish who desperately needs some food. However, when Mr. Krabs offers a meal at the Krusty Krab, Incidental 42 refuses, saying that there's no pizzazz. The fish then continues searching for food, water, and atmosphere.
In "Prehibernation Week," Incidental 42 whispers to Incidental 49: "This is a load of barnacles." Sandy somehow manages to hear him.
In "Club SpongeBob," Incidental 42 is with Nancy in the Kelp Forest where SpongeBob's clubhouse is seen flying past them. He tells Nancy to make a wish.
In "I Had an Accident," Incidental 42 plays football. Peterson Nat Tucker is the coach and says, "Nice catch, Percy!" Peterson then spanks Incidental 42 as a playful gesture, which scares SpongeBob. The pair are later seen next to each other in the seven-mile spanking machine.
In "Selling Out," when Mr. Krabs mentions the Krabby Patties are full of garbage, Incidental 42 says "What'd he say? Garbage?" and runs out of the restaurant.
In "Krusty Towers," Incidental 42 comes to the eponymous hotel and orders a double Krabby Patty with no onions and extra pickles. Mr. Krabs explains that customers need to rent a room and order room service if they want a patty. Incidental 42 looks at the time and explains "I only have an hour for lunch."
In "Wigstruck," one of the people who mock SpongeBob's wig, and then later wear a similar wig at the end.
In "Squid Wood," one of the customers at the Krusty Krab who cheer at Squid Wood's performance.
In "Good Ol' Whatshisname," Incidental 42 is named Isabelle and Marv when Squidward reads from the book of names.
In "The Play's the Thing," Incidental 42 asks Squidward for a Double Krabby meal with extra kelp. Later, Incidental 42 appears in an angry mob that angrily tells Squidward they want their Krabby Patties. Incidental 42 later pays Mr. Krabs to toss Krabby Patties at SpongeBob and Squidward.