Plankton discovers that Mr. Krabs hides the Krabby Patty secret Formula under the Krusty Krab floor boards, after Mr. Krabs trips over a lose nail, and goes to get it by caving in under ground, however he crashes into a big rock, and when he digs deeper to go around it he gets trapped in an underground cave. Plankton discovers its beautiful and comes up with plan on how he could get more customers, he'll lure them under ground by the gorgeous scenery of the cave. Later that day Mr. Krabs discovers that Plankton has more customers by his cave and decides to go down there to sell Krabby Patties. Plankton is mad about this and decides to get his revenge by trapping Mr. Krabs underground. The two end up fighting trying to get each other trapped under ground. They end up both getting stuck under ground and SpongeBob comes to save them. When he does, Plankton goes above ground again to steal the secret formula, but when he gets above ground he falls back down and so does the Krusty Krab and the Bikini Bottomies gets trapped, The episode ends with the Cave Dwellers and Plankton as Cashiers.Template:Section-Expand
( ‣ ) Associated production music
( • ) Original music
( ◦ ) SpongeBob music
•SpongeBob Theme - Jeremy Wakefield, Sage Guyton [title card] ‣Sailor's Sting 4 - Michael Bolger, Nicolas Carr ["Looky, another bright-eyed, bushy-tailed customer!"] •Vibe Q Sting - Nicolas Carr [secret formula hidden under Krabs' floor] ‣Zelle 501 and 3 - Gerhard Trede ["Did you see that?"/Plankton drilling underground] ‣Big Bad Giant - Paddy Kingsland [drill hits a rock] ‣Munitions Train - Harry Bluestone [Plankton tunneling under the rock] ‣Steel Sting (c) - Jeremy Wakefield [they fall into an underground cave] ‣Voyage of a Lifetime 1 - John Fox [pan of cave] ‣Cartoon Sting 3 - Gerhard Narholz [Karen gets an idea] •Harp Ding - Nicolas Carr ["Karen!"] •Horror House of Wax Retro 2 - Nicolas Carr, Ron Wasserman [cave dwellers] ‣Cellar Search - Philippe Pares ["From now on, you shall be my minions."] ‣Tiki Rapido - Lionel Wendling [cave turned into a restaurant] ‣Kommissar X - Gerhard Trede [cash register full of money] ‣Steel Link (c) - Jeremy Wakefield ["I'm running out of space for this stuff."] •Hawaiian Trax - Sage Guyton, Jeremy Wakefield [Patrick eating chum] ‣Symphonic Panorama - Gregor F. Narholz ["You come down here to admire the subterranean splendor of the chum caverns."] ‣Tiki Rapido - Lionel Wendling [gift shop] ‣Steel Licks (a) - Jeremy Wakefield [SpongeBob goes back to the Krusty Krab] • ? - Michael Bolger, Nicolas Carr ["Where have you been?"] ‣Battle March Link (f) - Keith Mansfield ["Krabs? What are you doing here?"] • ? - Michael Bolger, Nicolas Carr [SpongeBob selling Krabby Patties] ‣Enter the Villain - Chris Payne, Paul Rogers ["You can't just slither down here and steal all my customers!"] •Vibe Sting - Nicolas Carr ["Sea turtles, he called it!"] •Slide Whistle Song - Nicolas Carr, Sage Guyton, Jeremy Wakefield [Plankton, Krabs tunneling under each other] ‣The Great White - Gregor F. Narholz [Plankton and Krabs trapped underground] ‣Cartoon Sting 2 - Gerhard Narholz, Nicolas Carr, Barry Anthony [Plankton tries to escape] ‣Epic Tragedy - Gerhard Trede [Plankton and Krabs crying] ‣Tearjerker - Harry Bluestone, Emil Cadkin ["Let's agree to work together."] ‣ ? ["Hang on a minute."] ‣Film Fanfare (a) - Dick Stephen Walter [SpongeBob rescues them] •Vibe Q Sting - Nicolas Carr ["Where'd he go?"] •Grass Skirt Chase - Sage Guyton, Jeremy Wakefield [Plankton trying to steal the formula] ‣Sword Fight - Harry Bluestone, Emil Cadkin [everyone gets trapped underground] • ? - Michael Bolger, Nicolas Carr ["Satisfied with yourself, Plankton?"] ‣Tympup B - Sammy Burdson, John Charles Fiddy [ending] •Hawaiian Sting - Nicolas Carr [ending]
In this episode, the secret recipe is seen hid under a wooden plank floor in Mr. Krabs' office, but in the episode "Plankton's Army" Squidward says "Let me guess, it's at home, under your mattress," and Mr. Krabs rushes to his house. It is possible that he moved the secret recipe to his office after Squidward revealed where he hid it.
This is the second time people eat chum thanks to the attraction. The first was in "Chum Bucket Supreme."
This is one of few times SpongeBob enjoys eating chum as in the episode "Chum Bucket Supreme," he hates the taste of it.
During one part where Mr. Krabs and Plankton are digging underground, it may be a reference to the classic Namco arcade game Dig Dug, when they keep going under each other to make the other one fall.
In the Chum Caverns, there is no elevator shown going back up.
The first time the elevator is shown going down, eight people are enter it from ground level. The second time, only six people enter at ground level.
Plankton was on the surface at the end, but when the Krusty Krab fell underground, he was inside the Krusty Krab.
When Plankton first begun to dig the drilling tool was on a wire. In the next scene, it was attached to the vehicle. His vehicle was destroyed when he reached the Caverns. Then later in the episode it reappears, when Plankton was digging under Mr. Krabs.