SpongeBob wakes up one morning and finds out that Gary is missing, and discovers that he is the only one left in all of Bikini Bottom. At first, he finds this hard to take. In panic, he runs around town in a desperate attempt to find anyone, only to find nobody.
When the others do not return, SpongeBob decides to live out everyone's lives for them. He makes a bubble version of himself in his front yard, then runs to the top floor of Squidward's house, pretending to be Squidward yelling at SpongeBob for making too much noise. The latter then runs to the Krusty Krab, imitating Squidward and Mr. Krabs. He then imitates Sandy at her Treedome and Patrick in his rock before running to the boating school and pretending to be Mrs. Puff.
While in the classroom, he realizes that living out everyone's lives will not work, and breaks down crying on Mrs. Puff's desk. SpongeBob's mood quickly changes when he discovers a stack of blank driver's licenses. He takes a picture of himself, and prints out his own license. He then takes off with the student test boat, naming it "Boaty," and joyriding throughout the city.
SpongeBob and Boaty become inseparable best friends. The latter sleeps with the boat, and parks it inside both his house and the Krusty Krab. SpongeBob is going insane without people to talk to, and Boaty realizes this. In his closet, SpongeBob has erected a statue of Patrick out of raw Krabby Patty meat, which he carries out a conversation with. The "Patty-Patrick" warns him that he cannot talk because Boaty is listening. He goes crazy from the sight of any motor vehicle, and when a bus comes, he grabs a fire ax from the cinema to chop at the bus that approaches him.
To his surprise, everyone in Bikini Bottom comes out of it. Mr. Krabs tells SpongeBob that everyone's mysterious disappearance was really a holiday to celebrate being away from the latter for a day (according to SpongeBob, they were gone for weeks) called National No SpongeBob Day. Before venturing off, a giant effigy of SpongeBob is erected, and then burned. Everyone then dances on the ashes to celebrate. SpongeBob is deeply saddened by this but Mr. Krabs tells him that the holiday is an honor. Patrick recommends a "No Patrick Day." After Patrick says this, everyone celebrates National No Patrick Day and boards the bus except for Patrick, obviously forgetting what he just said.
In this episode, SpongeBob may have naviphobia, the fear of boats, due to the fact that the boat almost chases him.
This episode takes place after "Mimic Madness" because when SpongeBob imitates his friends he doesn't get "Mockin' Mimicry Madness."
SpongeBob is able to walk right into the Krusty Krab in the morning without Mr. Krabs unlocking the door. However, in episodes such as "The Lost Mattress" and "Once Bitten," Krabs is shown to have to unlock the door with a key so the employees can go inside. Perhaps he left it unlocked for SpongeBob to get in at this point.
This is the second time SpongeBob impersonates Mr. Krabs. The first time was in "Shell of a Man."
When SpongeBob looks for Squidward in his house, Squidward's 483 self-portraits from the sister episode "Not Normal" can be seen.
The way SpongeBob keeps repeating "go" to make it sound like an echo is just like how Patrick repeats "road" for the same reason in The SpongeBob SquarePants Movie.
The characters whom SpongeBob impersonates include:
In French, the title is "Une journée sans Bob L'éponge," which means "A Day without SpongeBob."
This is one of few episodes where no main characters other than SpongeBob play a significant role. SpongeBob is the only main character, not counting the ones he impersonates, who appears up until the end.
In the shot of the outside of SpongeBob's house with some wind blowing lots of leaves, the neighbor houses, such as Squidward and Patrick's houses, are missing.
SpongeBob's mouth does not move when he called for Patrick.
The lights in Squidward's house appear to be on when SpongeBob goes in to ask if he has seen Gary, but from outside windows, they are not on.
When SpongeBob is trying to keep Sandy's memory alive, he is not wearing his Water Helmet in Sandy's treedome and is able to breathe.
SpongeBob also does not take Sandy's shape as of everyone else.
When SpongeBob goes to his boating school, he is seen wearing a dress similar to that of Mrs. Puff. When he starts to get upset and sees the blank driver's licenses, he is seen wearing his normal clothes again.
When SpongeBob is driving Boaty around, he crashes into many things without giving the boat a dent or damage mark.
When SpongeBob puts Boaty on the patties to make Krabby Patties and floors it, only the wheel on the Krabby Patties moves, but the wheel on the other side does not move at all.
When SpongeBob gets his boat, said boat's seat is red, but when SpongeBob crashes into his house, wanting to sleep, the boat's seat turns purple.
When SpongeBob goes to sleep, Boaty is halfway in his pineapple, but later, it is in the bed with the former. However, it is possible that SpongeBob woke up once and placed it there off-screen.
When SpongeBob is talking to the Krabby Patty Patrick, Krabby Patty Patrick gets significantly smaller when the scene shows Boaty in the background.
The street lights and the theater are somehow on even though no one is in Bikini Bottom to turn them on. They may have been left on before everyone left, though.
It is unknown how the whole town could fit into a single bus. However, when the people come out of it is very full.
When everybody gets back on the bus, Gary, Sandy, and most of the other Bikini Bottomites are not seen.
At the end, SpongeBob becomes terrified of all vehicles, as Boaty is continually watching him, and he attacks the front of a bus with an axe. When everyone leaves for No Patrick Day, however, the axe is mysteriously gone.