SpongeBob and Patrick find that their television heroes, Mermaid Man and Barnacle Boy, are retired old people. SpongeBob and Patrick try to get them back into Superhero business again.

SpongeBob is awarded a prize for his life size Krabby Patty sculptures of Mermaid Man and Barnacle Boy. The prize is the "Magic Conch" as seen in many episodes of the television show "The Adventures of Mermaid Man and Barnacle Boy." The conch shell, when blown, will make a noise and Mermaid Man and Barnacle Boy will come running! It is meant only for danger. SpongeBob blows the conch for simple chores. Will the heroes be so annoyed they must take back the conch?

Mermaid Man and Barnacle Boy decide to go on vacation, but unfortunately they don't have anyone to look after the Merma-lair, so they ask SpongeBob and Patrick to look after it. However, they accidentally release Man Ray from a prison made of frozen tartar sauce.

After Mermaid Man accidentally drops his utility belt, SpongeBob finds it and can't resist trying it on.

After being treated too much like a child by everyone, Barnacle Boy quits being a superhero and decides to be a supervillain.

The adventures of Mermaid Man and Barnacle Boy are being told in a thrilling new motion picture. But after SpongeBob learns the heroes will be played by young actors, he sets out to make his own version of the movie using the real guys, fresh from their retirement home.

After SpongeBob reads a scary book before bedtime, he sees scary creatures in the dark.

After Plankton turns Mermaid Man and Barnacle Boy into his minions with his mind controlling device, he controls the heroes and orders them to encourage the customers of the Krusty Krab to eat at the Chum Bucket.

SpongeBob ditches boating school, then gets distracted on his way back.

SpongeBob and Patrick pretend to be their heroes at a shuffleboarding contest, but get sidetracked on the way home.

SpongeBob and Patrick accidentally change past events with Mermaid Man's time machine.

SpongeBob and Patrick watch a lost episode of The Adventures of Mermaid Man and Barnacle Boy.

SpongeBob and Patrick learn the secret origins of Mermaid Man and Barnacle Boy from the heroes themselves.

Plankton teams up with Man Ray to get the Krabby Patty formula and rule the world.