- SpongeBob SquarePants
- Patrick Star
- Sea whelks (debut)
- Mother sea whelk (debut)
- Incidental 48
- Incidental 107
- Incidental 37A
- Incidental 106
- Incidental 27
- Incidental 7
- Incidental 105
- Incidental 104
- Incidental 64
- Incidental 60
- Realistic Fish Head
- Gary the Snail (cameo)
- Incidental 36
- Squidward Tentacles
- Incidental 41
- Incidental 108
- Incidental 114
- Incidental 115
- Incidental 40
- Fred (blue)
- Eugene H. Krabs
- Incidental 4
- Incidental 37B
- Incidental 13
- Sandy Cheeks
- Margaret SquarePants (mentioned)
- Incidental 42
- Incidental 155
- Incidental 150
- Incidental 151
SpongeBob and Patrick are in Jellyfish Fields when they hear a strange noise. Soon, a stampede of large whelks make their way through Jellyfish Fields, destroying anything in their path. The whelks cover SpongeBob and Patrick in purple goo, which SpongeBob cleans up. As the whelks make their way to Bikini Bottom, SpongeBob and Patrick decide to warn the Bikini Bottomites about the whelks, but the whelks are already chasing and terrorizing everyone, blowing purple goo bubbles around their victims and swallowing the bubbles with their victims inside. SpongeBob and Patrick wonder what the whelks are.
Johnny Elaine explains them on TV, suddenly signing off the news when he is eaten by a sea whelk. Patrick claims that he is not scared of whelks and provokes one by blowing a raspberry at it, causing it to chase him and SpongeBob to the Krusty Krab. When they arrive, they warn Mr. Krabs about the coming danger. Soon after, the whelks make their way to the Krusty Krab, but Mr. Krabs thinks they are just plain old customers.
A larger mother whelk is then revealed, assisting her "babies." When Mr. Krabs offers them all Krabby Patties, the mother not only dislikes and spits them out but swallows him, along with Squidward and the entire Krusty Krab. SpongeBob and Patrick then run to Sandy's treedome, where Sandy only allows them to enter after confirming that they are not whelks. Sandy puts metal armor around the Treedome for protection against the whelks and tells SpongeBob and Patrick her plan to defeat the whelks.
Suddenly, the whelks crack and destroy the Treedome and SpongeBob, Sandy, and Patrick are swallowed by the mother whelk. Inside the whelk, Sandy discovers that the whelks are sick. SpongeBob then simply helps the whelk get better again by doing what he did to cure his suds, revealing the whelk's true form, a tiny, helpless whelk. SpongeBob does this to all the whelks and restores the whelks' happy family. All of the "eaten" victims are rescued, and the episode ends with Squidward complaining about all that just because the whelks "had the sniffles," then getting doused with purple whelk goo.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ The Creature (a) - Gregor F. Narholz [Title card]
• Aloha Lui Lui - Nicolas Carr, Sage Guyton, Jeremy Wakefield [Opening]
• Earl's Revenge - Sage Guyton, Jeremy Wakefield [SpongeBob and Patrick jellyfishing]
‣ Monster Bug A - Gregor F. Narholz [rumbling]
• Light Conversation 1 - Nicolas Carr, Barry Anthony [SpongeBob and Patrick covered in slime]
‣ Fight For Your Life! - Gregor F. Narholz [Whelks invading Bikini Bottom]
• Bikini Bottom News Theme - Nicolas Carr [news on TV]
‣ Drama Link (D) - Hubert Clifford [SpongeBob screams]
• Steel Sting - Jeremy Wakefield ["Hey, Gary."]
• Noodly Shenanigans - Nicolas Carr, Barry Anthony [Patrick teases a whelk/Patrick drinks a glass of water]
‣ The Creature (a) - Gregor F. Narholz [Whelk roars at him/SpongeBob and Patrick run to the Krusty Krab]
‣ Attack - Anthony Hymas [SpongeBob warning Krabs about the whelks]
• Great Idea Patrick - Nicolas Carr ["That means hungry!"]
‣ Monster Bug A - Gregor F. Narholz [Whelks approaching Krusty Krab]
• Jovial Pirate's Jig - Michael Bolger, Nicolas Carr ["Krabby Patties! Get your Krabby Patties!"]
‣ Monster Bug A - Gregor F. Narholz [Giant mother whelk appears]
‣ The Creature (a) - Gregor F. Narholz [Mother whelk eats Krusty Krab]
‣ Attack of the Giant Robots - Cris Velasco [Sandy lets SpongeBob and Patrick in]
• Karate Action - Nicolas Carr [Action-packed answer]
‣ Fight The Beast! [#20] - Gregor F. Narholz [Whelks invade treedome]
‣ Command Post 2 - Harry Bluestone, Emil Cadkin ["Follow me!"]
‣ Death Throws [#9] - Harry Bluestone, Emil Cadkin ["I guess this is it, Patrick."]
‣ Fight The Beast! [#20] - Gregor F. Narholz [Mother whelk eats Sandy, SpongeBob and Patrick]
‣ Desperate Situation - Phil Green [SpongeBob and Patrick inside the whelk's stomach]
‣ Fighting Legions A - Gregor F. Narholz ["The Krusty Krab!"]
• Vibe Q Sting - Nicolas Carr ["Hmm..."]
‣ Sneaking About - Phil Green [SpongeBob and Patrick lend Sandy their corneas]
‣ Lonely Stranger - Laurie Johnson [Sandy examining the whelks' slime under a microscope]
• Steel Licks 20 - Jeremy Wakefield ["I know just what to do!"]
‣ Lionheart - Larry Hochman [SpongeBob absorbing the whelks' snot]
• Lap Steel - Nicolas Carr [SpongeBob laughs]
• Wahini Wobble Faster - Nicolas Carr, Sage Guyton, Jeremy Wakefield [Ending]
- This episode is available on the Complete Seventh Season, SpongeBob SquarePants Vol. 11, Beware the Hooks, It Came from Goo Lagoon, The SpongeBob SquarePants Collection, The SpongeBob SquarePants 8 Season DVD Collection, Next 100 Episodes, and The Best 200 Episodes Ever DVDs.
- This episode preceded the series premiere of the Nickelodeon animated series Planet Sheen and T.U.F.F. Puppy.
- It is revealed that SpongeBob's mother's maiden name is "BubbleBottom."
- Even though the episode focuses mainly on the whelks, there appear to be sea urchins on the title card.
- In this episode, to put a metal shield over her treedome, Sandy presses a button on her tree, but in "Texas," it was a lever.
- The metal sheeting also goes much slower in this episode than it did in "Texas."
- It could be that Sandy has made adjustments to her treedome.
- SpongeBob references the episode "Suds" when he says, "After all, I've had the suds."
- This episode reveals that SpongeBob's water helmet acts as a replacement helmet for Sandy.
- When Sandy lets in SpongeBob and Patrick, she's wearing her spacesuit, but when they're all in her treedome, Sandy is in her bikini. Sandy removes her spacesuit offscreen when they arrive at her treedome.
- When Sandy uses SpongeBob's helmet, it does not have a flower on the top, but when Sandy is at the Krusty Krab in the whelk's stomach, the helmet has a flower. Sandy may have found a flower when she was swallowed by the whelk.
- This episode is one of two episodes in season seven to use the Crowd Scream sound effect, the other being "SpongeBob's Last Stand."
- During the Craziest Creatures marathon, it was paired up with "The Krabby Patty That Ate Bikini Bottom."
- For a SpongeBob airing on October 20, 2020 at 11 PM EDT, this episode aired with “Survival of the Idiots”. 
- When the tower is raising from the Krusty Krab, in one frame, SpongeBob has his uniform hat on; while in the previous and following frame, he does not.