The episode begins at SpongeBob's house during a wind storm warning, 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 while Squidward was watching male ballet, but the wind destroys his house too, at that point, all TVs are broken due to weather, 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 tried to tell them about the Big Splash that formed the seven seas but that wasn't related the origin of the crime fighting duo. Mermaid Mans tells the story that 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, random 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 breathe 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.
During a tour of Rough Draft Korea for students of Yongsan International School of Seoul in 2016, various SpongeBob color background books were discovered for many episodes. One of the books found was created for "Mermaid Man Begins."[6]
This episode is alternatively titled "Mermaidman Begins."[1]
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.
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.
