SpongeBob introduces Gary to Patrick by playing tag, and they then decide to have a sleep-over together. The next morning, Gary apparently doesn't want to leave Patrick, who concludes that Gary wants to be with him and claims him as his own pet. SpongeBob refuses to believe this, but when Gary is left with the choice of who to be his owner, Gary chooses Patrick. SpongeBob is heartbroken, and out of jealousy, he attempts to find a new pet to show to Gary that he doesn't need him.
At first, he gets Rex, a worm. SpongeBob goes up to Patrick and Gary (who do not appear to know he is there) and after introducing Rex starts listing all the reasons why worms are better than snails. Rex, however, immediately abandons him and leaves on a bus. Next, he gets Lary, a wild snail. SpongeBob tells Lary that Gary will not be mentioned in the house, and uses Gary's bowl for Lary (with the G crossed out). Lary, however, acts viciously hostile toward him, and is presumably kicked out.
Later, Patrick and Gary come to SpongeBob's house to do his laundry, resulting in the former and latter getting into an argument. While this happens, Gary crawls into the washing machine after Patrick's pants. SpongeBob and Patrick inspect this, and Patrick initially thinks that Gary only liked him because of his pants. SpongeBob, however, realizes that Gary just wanted the cookie in Patrick's pocket. As SpongeBob and Gary, now reunited, go outside for a walk, a heartbroken and defeated Patrick stares after them and shouts, "Gary? I thought what we had was special!"
This is the first time SpongeBob says "Gary the snail!" to Gary in the series.
When the camera zooms in on SpongeBob thinking, Patrick is saying "Blah, Blah, Blah" in the background. When the camera zooms out Patrick is speaking normal again, but when SpongeBob leaves Patrick's rock, he says "Blah, Blah, Blah" again.
This is the first episode to show Patrick as the main antagonist.
SpongeBob, in a throwaway joke, reveals that he has another pet snail, "Jerry," a photo-realistic land snail.
SpongeBob reminds Gary that he took care of him when his eyeballs were sore. Closed captions alternate between "sore" and "tore" in different airings.
A smaller version of SpongeBob's wringer can be seen when Patrick is placing his basket of clothes on the table.
When the time lapses from night to day right after the "sleepover," a human finger is visible in the water right below the island, this is because the island is in Tom Kenny's pool.
In the beginning, SpongeBob is playing tag with Gary. When he runs up his house, an extra window is seen next to the upstairs window. The extra window reappears at the beginning of the scene where SpongeBob introduces Rex.
Rex, SpongeBob's pet worm leaves on a bus. In early airings, this bus had obvious jellyfishers on it. By default, that makes this currently the final epsode to feature a bus full of jellyfishers.
The face SpongeBob makes when he says "Who's a good boy?!" to Rex can be seen on various SpongeBob licensed products, including the newer packages of SpongeBob-shaped Kraft macaroni & cheese. It's accompanied by the slogan, "grin and square it!"