Arthur, Buster, and D.W. want to protect a sand castle they built at the beach.
Tropes for "Swept Away" include:
- Beach Episode: Over the summer, Arthur, Buster, and D.W. go on a beach trip.
- Bittersweet Ending: Castle Starfish gets swept away by the tide, as Arthur and Buster reflect as the summer ends. However, D.W. reveals to the audience that she has kept the starfish from atop the castle as a souvenir, turning it into a necklace.
- Failure Montage: When Arthur, Buster, and D.W. try to rebuild Castle Starfish, they run into problems when they can't find good quality sand and their defenses get washed away by the tide.
- Five-Second Rule: Buster's friends are grossed out by his "sloppy" habits, one of which is eating food that he dropped on the floor, justifying it with the five-second rule.
- Immediate Self-Contradiction: D.W. complains about the name "Starfish Enterprise":D.W.: "Enterprise"? I can't even say that word!
Arthur: You just did.
D.W.: Well, I don't like it! - I Was Having Such a Nice Dream: Arthur has a dream where he and Buster, the kings of Castle Starfish, manage to successfully stop an incoming wave. As the citizens cheer Arthur's name, it turns out to be D.W. calling for him, waking him up to ask if the castle will be okay.
- Removable Shell: In Arthur's dream, King Buster declares that they will reinstate "casual day", meaning snails can go to work without wearing their shells.
- Seahorse Steed: In Arthur's dream, D.W. translates the words of a sea horse trying to communicate with Arthur and Buster. The sea horse makes neighing sounds like a land horse.
Buster becomes afraid of germs.
Tropes for "Germophobia" include:
- Book Ends: The peak of Buster's dirtiness is shown when he plays a harmonica he finds in the trash. At the end, Buster's friends gift him a new harmonica. He cleans it with a wipe first, and then plays a note.
- Imagine Spot: The episode regularly shows Buster's imagination, of his classmates expelling foul green clouds and germs appearing everywhere.
- Got Volunteered:
- Francine, Muffy, and Sue Ellen make Arthur tell Buster how unclean he is, forcing him to do it simply because he's Buster's best friend.
- Later, at the pool party, they want someone to tell Buster that his Neat Freak tendencies are ridiculous. They all stare at Arthur, but subverted in that he refuses.
- Neat Freak: Buster becomes one when Brain scares him by showing that germs are everywhere. He wraps his lunch in excessive amounts of plastic wrap, wears hockey gloves before touching anything, and washes his hands compulsively.
- The Pig-Pen: Buster's gross habits are exaggerated in this episode. He doesn't take baths, doesn't wash his hands after using the bathroom, and at one point uses a harmonica he finds in the trash! It takes him being told how germs are everywhere to snap him out of this, but then he goes too far in the opposite extreme and becomes a Neat Freak instead.
- Sealed Evil in a Can: How Buster views the harmonica he finds in the trash. During a dream sequence, he sees it shining at the bottom of the pool. Buster grabs it and plays it, unleashes a large cloud of germs that scare away his friends.
- Terrified of Germs: Buster. He goes too far with his fear that it prevents him from having any fun at his own pool party, although he does get over it when he accepts that there are good germs in his body as well.
