- French Narrator
- Sandy's pets
- Patrick Star
- SpongeBob SquarePants
- Sandy Cheeks
- Sea urchins
- Squidward Tentacles
- Eugene H. Krabs
- Incidental 49
- Incidental 154
- Incidental 31
- Incidental 93
- Incidental 73
- Incidental 8
- Incidental 22
- Incidental 5
- Incidental 65
- Incidental 39
- Incidental 150
- Incidental 23
- Incidental 45
- Incidental 18
- Incidental 41
- Incidental 64
- Incidental 12
- Incidental 36
- Incidental 27
- Incidental 42
- Incidental 3
- Incidental 48
- Incidental 9
- Incidental 67
- Incidental 7
- Incidental 91
- Incidental 68
- Incidental 15
- Incidental 6
- Incidental 37B
- Incidental 46
- Yellow with blue stripes
- Incidental 60 (cameo)
- Incidental 85
- Incidental 25
- Incidental 32
- Incidental 17
- Incidental 11
- Incidental 16
- Incidental 47
- News caster (voice only)
- Gray fish (debut)
- Fire fish
- Incidental 84
- Incidental 20
- Incidental 69
- Incidental 21
- Incidental 115
- Incidental 10
- Incidental 92
- Incidental 37A
- Incidental 2
- Incidental 33
- Other Bikini Bottomites
SpongeBob and Patrick are given the task of pet-sitting Sandy's pets while she is out of town. One of the many animals left in their care is a small Monarch caterpillar named Wormy. Despite it requiring the least attention, SpongeBob and Patrick quickly befriend the caterpillar and enjoy a day of play together. As the two leave, they vow to have even more fun with Wormy the next day.
Overnight, Wormy goes through quick metamorphosis and becomes a monarch butterfly. When they return the following morning, SpongeBob and Patrick search for their new friend but merely see what looks like a beautiful winged creature instead. Upon opening the jar and finding only Wormy's discarded chrysalis and best friend ribbon inside, they come to the grim conclusion that this "horrific beast" has devoured Wormy and is now on the loose. They try to trap the supposed monster by disguising Patrick as bait. When this fails, SpongeBob manages to encase the butterfly in a bubble and releases it outside the treedome, in attempt to "save" Sandy's pets. However, now the butterfly is loose in Bikini Bottom, so SpongeBob and Patrick chase after it.
Beating the creature to the Krusty Krab, SpongeBob warns Mr. Krabs and Squidward, both of whom scoff at the tiny insect. However, with one good look at its face, the two are scared senseless and run away, their discarded undergarments leaving SpongeBob and Patrick to believe they were also eaten.
SpongeBob and Patrick begin to spread news of the "terrible monster" throughout Bikini Bottom. Mass chaos erupts with every tiny flap of its wings, and as a result of the people's hysteria, the whole town ends up destroyed in a fire.
A few days later, Sandy arrives back at the ravaged town, saying that it looks like a twister hit it and wonders where everyone is. Wormy then flies up to her and she recognizes him, saying that he wasn't supposed to change until her return, and places him inside a jar. All the townsfolk cheer and celebrate the capture of the so-called monster, Sandy believing it to be just because they missed her that much, and thinks maybe she should go out of town more often.
- Wormy's close-up in his butterfly form.
- Everyone getting scared of Wormy as a butterfly and mistaking it for a monster.
- Chaos spreading all over Bikini Bottom.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
• 12th Street Rag - Sage Guyton, Jeremy Wakefield [Title card]
‣ Dreamy Hawaii - Terry Day [opening]
• Earl's Revenge - Sage Guyton, Jeremy Wakefield [Sandy's pets]
‣ Children 2 - Dave Hewson ["Hey, little fella."]
• Puka A - Sage Guyton, Jeremy Wakefield [playing hide, seek]
◦ That's What Friends Do - Peter Straus
‣ Youthful Days - Mike Sunderland ["Gee, SpongeBob, I don't want today to end ever."]
‣ Code Dead End - Gregor F. Narholz [Wormy turning into a butterfly]
‣ On the Beach - Kapono Beamer ["Here I come, Wormy!"]
‣ House of Horror - W. Merrick Farran ["I think something bad happened to Wormy."/SpongeBob and Patrick scream.]
‣ Flight in Panic 1 - Gregor F. Narholz [SpongeBob and Patrick running to the door/SpongeBob and Patrick running backwards]
‣ Hangman (b) - Dave Hewson ["Now what?"]
‣ Action Cut A - Gregor F. Narholz ["He's eaten Patrick!"]
‣ Footsteps of Horror - W. Merrick Farran [phone in jar/Patrick on a dinner plate/Patrick runs away]
‣ Death Trap - Gregor F. Narholz [SpongeBob traps the butterfly in a bubble]
‣ Bridgehead Alt. End - Sam Fonteyn ["Yeah!"]
‣ Lovely Scenery (c) - Mladen Franko ["...headed straight for the Krusty Krab!"]
‣ Hit and Run - Sam Spence [secret entrance]
‣ Frankenstein's Niece A - Gregor F. Narholz [SpongeBob warns Krabs about the "monster"]
‣ A Sad Affair - Mike Sunderland [SpongeBob and Patrick crying]
‣ Frankenstein's Niece A - Gregor F. Narholz ["That's the monster?"]
‣ The Rake Hornpipe - Robert Alexander White ["Get a load of the scary monster."]
‣ Frankenstein's Niece A - Gregor F. Narholz [Squidward and Krabs scream/"It ate them! And there it goes!"]
• Harp! - Nicolas Carr [thumbs up]
• Sea Weed - Steve Belfer [SpongeBob, Patrick warning everyone]
• 12th Street Rag - Sage Guyton, Jeremy Wakefield [everyone running from the butterfly]
‣ Bridgehead Alt. End - Sam Fonteyn [ending]
- This episode is available on the Nautical Nonsense and Sponge Buddies, Christmas (Polish only), Complete 2nd Season, Sponge Buddies, Imitation Krabs, The Ultimate SpongeBob Box Set, Really Big Box Set, The SpongeBob SquarePants Collection, The SpongeBob SquarePants 8 Season DVD Collection, Sponge Crazy, First 100 Episodes, SpongeBob SquarePants Vol. 2, The Complete Second Season, From the Beginning, Pt.1, SpongeBob SquarePants Has Hit Rock Bottom, The First & Second Seasons, and The Best 200 Episodes Ever DVDs.
- This episode is available on the Sponge Buddies and Undersea Antics Volume 1 VHS tapes.
- This episode is also available on the It's a SpongeBob Christmas! Blu-ray.
- "Wormy" was ranked #57 during the Best Day Ever event from November 9–10, 2006.
- "Wormy" was ranked #43 during the SpongeBob's Top 100 event in the UK and Ireland from June 4-8, 2012.
- The working title for this episode was "Shoo Fly."
- At the beginning, Patrick whistles and SpongeBob remarks "I didn't know you spoke bird," to which Patrick replies, "No, that's Italian, SpongeBob." In the Italian version, he says that it is Spanish.
- The quote "Why does this keep happening to me?!" was later used in the online game Dirty Bubble Busters.
- Wormy is able to complete the full transformation from a caterpillar to butterfly in just one night. In real life, this is impossible, and the length varies with different species of butterfly. In Wormy's case, Monarch butterflies spend 10 to 16 days in the chrysalis stage when changing into a butterfly.
- Sandy lampshades this by saying "You weren't supposed to change 'till I got back."
- This is the first episode where Sandy's tail is out of her diving suit, right after season 1 as her tail was inside of her diving suit.
- There are three books based on this episode called Wonderful Wormy, Salty Sea Stories, and Wormy.
- The warning poster SpongeBob and Patrick put up depicts a Viceroy butterfly, while Wormy is actually a Monarch butterfly. Viceroys belong to a different family group of butterflies and are smaller and less common than the Monarchs. The reason why Viceroys resemble Monarchs is due to Müllerian mimicry, in which two separate species that share a certain predatory defense mechanism. In this case, tasting bad to birds also shares very similar warning patterns.
- This is the 50th episode segment in the series in both production and premiere order.
- When SpongeBob stands on a treasure chest, warning people about the butterfly, the word "Dogs" can be seen on a building in the background.
- During the Craziest Creatures marathon it was paired up with "Frankendoodle."
- Plots of this episode were later used in the second part of the LeapPad Interactive Book and Cartridge SpongeBob SquarePants Salty Sea Stories, which was released in 2003 by LeapFrog Enterprises.
- In the LeapPad adaption of this episode, there is an extra scene at the end where Sandy reveals the "monster" was Wormy all along, and SpongeBob and Patrick are relieved.
- This is the first episode to permanently feature Patrick's current design, featuring thicker eyebrows in a "Z" shape, instead of the original "M" shape.
- This is the first episode to feature a shortcut to the Krusty Krab.
- "My leg!:" After seeing a butterfly that is attacking Bikini Bottom on the newscast, Fred runs out of his house and falls on the ground.
- When SpongeBob says "We did it, Patrick!" during the destruction scene, a meteor can be seen flying down until it falls off-screen in the background for a few seconds later, at which point a flash can be seen in the background, referencing the landing explosion.
- This episode and "Patty Hype" were banned in some countries, due to the butterfly close-up frightening young viewers.
- This episode marks the second time that the Krusty Krab cash register boat operates like a vehicle. The first time was in "F.U.N."
- The live-action insect footage used throughout this episode are all royalty-free, and owned by Oxford Scientific Films. All of the footage can be found on Getty Images.
- This episode was paired with "Survival of the Idiots" during the Massive Monster Mayhem Marathon.
- After running away from the Krusty Krab, neither Squidward nor Mr. Krabs appear again for the remainder of the episode.
- This is the first episode to play "Code "dead End"".
- When Wormy's face is viewed as a close-up in butterfly form, the wrong insect is shown. As Wormy is a butterfly, there should have been circular black eyes, long antennae and a proboscis (tongue). Instead, enormous, rainbow-colored, shimmering eyes, sharp mouthparts and horn-like antennae are seen, distinctive to that of a horsefly. Furthermore, butterflies do not make buzzing sounds, which, again, is a characteristic of flies.
- For the scenes with Sandy, her acorn is black instead of its usual color.
- When SpongeBob begs Wormy not to eat him, his mouth does not sync correctly.
- Squidward's Krusty Krab employee hat is missing when Mr. Krabs asks "What's the meaning of this, SpongeBob?!"
- At the end of the Krusty Krab scene, SpongeBob's front teeth are connected for a few frames.
- When the final shot of Sandy is shown in her bikini before she leaves the treedome., but in the next shot, she is wearing her spacesuit and helmet.
- SpongeBob is able to blow a bubble in Sandy's treedome, despite the fact that he is wearing a water helmet.
- When SpongeBob collects the bubble soap with his bubble wand, the cap is still on the container.
- When Patrick warns everyone about the "monster," his mouth does not sync correctly.
- During some of the high-speed actions that take place in Sandy's treedome, bubbles are seen floating around. This cannot be possible, because Sandy's treedome is not filled with water.
- At the part where SpongeBob and Patrick run away from Wormy along with everyone else, the town is destroyed, but when they reach the stoplight while being chased, the town is perfectly fine.
- Incidental 7's dress changes from yellow to gray at one point when the Bikini Bottomites are being chased by Wormy as a butterfly.
- When Patrick is with the people holding up SpongeBob and Sandy, he does not have eyebrows. In another shot during the same scene, he does not have eyes.
- Also, SpongeBob's buck teeth and Sandy's left arm disappear for a split second.
- In addition, he is floating and Sandy's badge is also gone.
- Fred's eyes become transparent while carrying Sandy and SpongeBob at the end.
- When Mr. Krabs and Squidward scream, they are out of sync.
- When SpongeBob and Patrick first see Wormy's close-up, they both scream and run in opposite directions from each other. Then in the very next scene, they are shown hiding from Wormy in the exact same spot behind the picnic table.
- When SpongeBob and Patrick are about to hide behind the table from Wormy, SpongeBob's left arm disappears.
- When SpongeBob says, "Eh, sorry, I don't speak Italian," his eyelashes disappear for a split second.