- SpongeBob SquarePants
- Patrick Star
- Mermaid Man
- Barnacle Boy
- Squidward Tentacles
- The Ballet Dancer
- Two mermaids
- Dirty Bubble
- Man Ray
- Realistic Fish Head (voice only)
- Human captain (debut)
- Human scientist (debut)
- Alien spaceship (debut)
- Gary the Snail (cameo)
- Moth (cameo as an action figure)
- Jumbo Shrimp (cameo as an action figure)
- Pi-Right Ponderer (cameo as an action figure)
- Bikini Bottomites
The episode begins at SpongeBob's house during a nasty wind storm, where he and Patrick are preparing to watch the Mermaid Man and Barnacle Boy marathon on television. The marathon kicks off with an origin special, but just as it begins, SpongeBob's house loses power and a strong wind blows the house and the TV away. SpongeBob and Patrick go to Squidward's house, but the wind destroys his house too, so they decide to go to the Mermalair to ask the heroes about their origin personally.
Once they are there, Mermaid Man tells them the story. He was once a regular human being who was washed into the ocean and sucked into a whirlpool. Before he could drown, mermaids came and gave him a magical starfish that enabled him to breathe underwater. Shortly after, Mermaid Man saw Barnacle Boy scraping some barnacles off a ship's hull and thought that he was drowning. He used his newfound powers to draw barnacles into Barnacle Boy's lungs, allowing him to breathe underwater as well. They then decided to become a crime-fighting duo, though Barnacle Boy argues that this was only because he was stuck breathing underwater forever as a result of Mermaid Man's actions. The two heroes go on to talk about some of their earliest rescues, but soon begin to argue about what really happened.
Just then, the actual origin special appears on the Mermalair's giant monitor. In the special, after cooking popcorn for movie night, Mermaid Man and Barnacle Boy (called Ernie and Tim respectively) are thrust into a series of nonsensical, improbable events. Once they return to their apartment, the overcooked popcorn strikes the two with a jolt of cosmic energy, giving them superpowers and the urge to fight crime underwater. They dive into the sea and start fighting crime.
After the show ends, SpongeBob and Patrick put popcorn into a microwave with the intention of overcooking it and giving themselves powers of their own, and Mermaid Man and Barnacle Boy try to stop them.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
• Mermaidman and Barnacle Boy Action Theme - Michael Bolger, Nicolas Carr, Pat Irwin [Title card]
‣ Arizona Fanfare - Jack Shaindlin [TV show]
• Mermaidman and Barnacle Boy Action Theme - Michael Bolger, Nicolas Carr, Pat Irwin [SpongeBob and Patrick go over the checklist.]
‣ Arizona Fanfare - Jack Shaindlin [Mermaid Man watch]
‣ Crime & Danger Sign #3 - Hans Conzelmann, Delle Haensch [Start of marathon]
• Heroes to the Rescue - Nicolas Carr, Barry Anthony ["And now, without further fanfare..."]
‣ ? [fanfare]
‣ Excited Chase 1 - Phil Green [The pineapple blows away.]
• Watching Grown Men Prancing Around - Nicolas Carr, Marcin Pospieszalski [Squidward is watching ballet.]
‣ Excited Chase 1 - Phil Green [Squidward's house blows away.]
• Great Idea Patrick - Nicolas Carr ["Hey, that's it!"]
• Hot Steel and Slide Licks 5A - Jeremy Wakefield [Squidward blows away.]
‣ Against All Odds - Paul Lawler ["We have found the Mermalair!"]
‣ Fall to the Death - Harry Lubin [SpongeBob and Patrick fall into a net.]
• Lap Steel - Nicolas Carr ["Again!"]
• Befuddled - Pat Irwin [SpongeBob and Patrick laugh.]
• In the Beginning - Nicolas Carr, Marcin Pospieszalski ["In the beginning it was all dark."]
• Sponge Surf No Guit Me - Billy Lincoln, Michael Gurley [Young Mermaid Man surfs.]
• Mermaidman Hit - Nicolas Carr [BITE!]
• Aloha Lui Lui - Nicolas Carr, Sage Guyton, Jeremy Wakefield ["There I was in the ocean."]
‣ Dramatic Bridge 4 - Phil Green ["A wave drew me back into the ocean."]
‣ Dramatic Bridge 7 - Phil Green [Mermaid Man falling in the ocean]
‣ Rainbow Delights - Magnum Opus ["I was rescued by mermaids!"]
• Hot Steel and Slide Licks 2C - Jeremy Wakefield [Mermaid Man falls asleep.]
• Breathing Underwater - Nicolas Carr ["There I was in the ocean."]
‣ Mount Olympus - Paddy Kingsland ["I had no other humans to talk to."]
• Sad Sack Shanty - Michael Bolger, Nicolas Carr [Mermaid Man sees a ship.]
‣ Masked Crusader 2 [#21] - Harry Bluestone, Emil Cadkin ["A boy in trouble!"]
‣ Pirate Ship - Harry Bluestone, Emil Cadkin ["Fear not, young man"]
• Hot Steel and Slide Licks 6A - Jeremy Wakefield ["No, no, no."]
‣ Arizona Fanfare - Jack Shaindlin ["Mermaid Man and Barnacle Boy!"]
‣ Mermaidman and Barnacle Boy Action Theme - Michael Bolger, Nicolas Carr, Pat Irwin [A bank robbery occurs.]
‣ Heroes Salute - Harry Bluestone, Emil Cadkin ["Thank you, sir."]
• Mermaidman and Barnacle Boy Action Theme - Michael Bolger, Nicolas Carr, Pat Irwin [Barnacle Boy defeats Man Ray.]
• Hot Steel and Slide Licks 7A - Jeremy Wakefield [Mermaid Man orders a pizza.]
‣ Arizona Fanfare - Jack Shaindlin [TV comes back on.]
‣ Sprightly Link 6 - Harry Bluestone, Emil Cadkin [Winchell Apartments exterior]
‣ The Bachelor Life (a) - Laurie Johnson ["Come on, Ernie, the movie's about to start."]
‣ Lost in the Galaxy [#35] - Harry Lubin [A scientist is doing tests.]
‣ Battle Zone - Harry Bluestone, Emil Cadkin [Ernie and Tim fall out of their apartment.]
‣ The Bachelor Life (a) - Laurie Johnson [Movie night]
‣ Imminent 4 - Harry Bluestone, Emil Cadkin [Reaction to overcooked popcorn]
• Mermaidman and Barnacle Boy Action Theme - Michael Bolger, Nicolas Carr, Pat Irwin [Ernie and Tim become Mermaid Man, Barnacle Boy.]
• Hot Steel and Slide Licks 8A - Jeremy Wakefield ["Ah, feels just like yesterday, doesn't it?"]
• Slide Whistle Stooges - Nicolas Carr, Sage Guyton, Jeremy Wakefield [The ending]
- This episode is available on The Complete Eighth Season, Mermaid Man & Barnacle Boy: Defenders of the Deep, The SpongeBob SquarePants Collection, Home Sweet Rubble, The SpongeBob SquarePants 8 Season DVD Collection, SpongeBob SquarePants Vol. 13, The Best 200 Episodes Ever, The Adventures of SpongeBob SquarePants, and Next 100 Episodes DVDs.
- The origin special states that Mermaid Man and Barnacle Boy's real names are Ernie and Tim. These are nods to their respective voice actors, Ernest Borgnine and Tim Conway.
- However, in "Mermaid Man and Barnacle Boy V," Mermaid Man calls Barnacle Boy "Kyle."
- This is the first episode in the SpongeBob SquarePants series in which the humans and the surface world are fully animated and do not appear in live-action form.
- This was the last episode to feature Ernest Borgnine before his death on July 8, 2012. Two later episodes, "Super Evil Aquatic Villain Team Up is Go!" and "Patrick-Man!," were produced before his death and aired after.
- The episode's name is a reference to the 2005 DC Comics movie Batman Begins.
- Mermaid Man mentions an event known as "the Big Splash" which formed the sea. This is a parody of the Big Bang.
- The radioactive ant biting Ernie's forehead mirrors Peter Parker (Spider-Man) getting bitten by a radioactive spider in the Spider-Man series.
- The name of the Vats of Acid "R" Us factory is a reference to the toy store Toys "R" Us.
- The bomb that explodes on Mermaid Man and Barnacle Boy is a reference to how Bruce Banner became the Hulk.
- When Squidward's power goes out, his TV turns off, but his lights do not.
- Squidward's flooring appears smaller after his house is blown away.
- The narrator of the origin special mentions a solar eclipse, but it is actually a lunar eclipse, as the scene takes place at night.
- In the origin special, Ernie is bitten by a radioactive ant specimen in "the apartment directly above," but when he and Tim are flung back to their apartment, their window is shown to be on the top floor.