SpongeBob and Patrick play Mermaid Man and Barnacle Boy, in their costumes. They drive in the invisible car and think Squidward's house is an evil lair. They climb and Squidward sees them and cuts their rope, falling to the ground. They think Squidward is Dr. Negative, while Squidward sings a song about how much he hates his neighbors.
Squidward is then seen watering his garden, who SpongeBob and Patrick think is raising mutant vegetables to attack. While Squidward goes to refill his water, SpongeBob and Patrick destroy Squidward's garden, making a salad and eating it, which angers Squidward in the process. He breaks his legs in frustration, but loses balances and falls down.
At the Krusty Krab, SpongeBob and Patrick sing the Mermaid Man/Barnacle Boy song, annoying Squidward. He tells them the song is stupid, causing SpongeBob and Patrick to transform into their costumes and call him Dr. Negative again. Patrick thinks that a nearby fish has been injured but really just has toilet paper attached to his foot from the bathroom. Patrick gets out his first aid kit and they mummify the fish and put him in a wheelchair. Patrick then burns the fish's eyes with peroxide. Angered, the fish moves away. Squidward then tells them they have to take the trash out.
SpongeBob and Patrick punch the trash and it lands on the customers and they leave angered. Mr. Krabs is angry that all his customers are gone and he calls Squidward into his office. He shows his secret room, with comic books, and also with a suit that Krabs sewed up himself. Krabs then puts on the suit, called Captain Tightwad, with Squidward playing the doctor. Krabs sends out lassos to attack SpongeBob and Patrick, but all miss. He then throws Squidward at SpongeBob and he gets stuck. He manages to break free, but spins out and knocks objects, including money. SpongeBob then questions their fighting and opens up his comic book, which states that no superhero should fight a bad guy until the bad guy commits a crime. Mr. Krabs then steals his own money, but SpongeBob isn't stupid to realize that.
The setting then changes to a bank, where Krabs pretends to rob the bank. An old man tells him that the ATM is outside but then attacks Squidward and Krabs after they said they were pretending to rob the bank. At night, the Krusty Krab, now called the Lair, has transformed into a scientific evil lab. SpongeBob has a crime scene set so they can play, but Squidward takes it seriously, thinking it's his chance to knock his neighbors out. He actually lowers the lever on the trap sending SpongeBob and Patrick down towards boiling grease. Squidward wants them to fry but Krabs gives up because Squidward is literally playing the bad guy. SpongeBob and Patrick free themselves by tipping the lift, but Squidward and Krabs get fried and the Krusty Krab is now destroyed.
In the end, Krabs sticks to reading comic books and SpongeBob and Patrick fake drive into the distance. The TV Announcer says he needs to find another job and says if it is too late to go back to college radio.
The episode name was confirmed in a tweet by a crew member, Vincent Waller on July 16, 2016. A video from the Nickelodeon Italy YouTube video revealed the date when the episode was finished to be September 22, 2016. 
This is the second time that Mr. Krabs is Captain Tightwad. The first time was in the short "And Krabs Saves the Day."
However, in this episode, Mr. Krabs calls the hero Captain Tightwad, but in the short, "And Krabs Saves the Day," he calls the hero Super Tightwad.
This episode was paired with "Snail Mail" during its first airing in the United States.
On DirecTV, this episode is listed in Season 9, Episode 29, instead of Season 10, Episode 1. Its sister episode, "Whirly Brains," shares this trait.
Additionally, on DirecTV, it is named "MermaidPants."
This is the same for Comcast and Xfinity.
This episode premiered in Canada on the same day as the USA. This is the second time an episode aired in Canada on the same exact day as the American airdate, the first being "It's a SpongeBob Christmas!"
This episode and "Whirly Brains" are the only Season 10 episodes to premiere in 2016.
The scene when SpongeBob says "Do you expect me to cry?" and Squidward replies "No, Mr. Bob. I expect you to fry." is similar to a James Bond film Goldfinger where the villain attempts to kill James Bond.
When SpongeBob and Patrick wrap the customer with the bandages and put him in a wheelchair, SpongeBob's lips are moving but he doesn't say anything. However, this was probably because SpongeBob could be heard singing (dum dum dum...) really quietly while wrapping the bandages.
When the Krusty Lair is cracking and about to get destroyed, the sign says "The Krusty Krab" instead of saying "The Krusty Lair."