This is a work of thinly disguised (or sometimes entirely undisguised) nonfiction, written as a dialogue. Usually these dialogues feature a Mr. Exposition, who either explains the topic to The Watson or debates it with a Straw Loser. In either case, Mr. Exposition's partner is supposed to be bringing up the objections or points of confusion that the reader might have.
- Seen in DodgeBall: A True Underdog Story when the Average Joes are being taught Dodgeball by Patches O'Hoolihan on a VHS tape.
- Gödel, Escher, Bach: An Eternal Golden Braid starts each chapter with a dialogue like this, between Achilles (The Watson) and the Tortoise (Mr. Exposition). They're modeled on a similar dialogue, "What the Tortoise Said to Achilles", written by Lewis Carroll (in which Achilles is more of a Straw Loser, though he comes round in the end).
- How to Teach Physics to Your Dog by Chad Orzel is a quantum physics popularization featuring the author himself as Mr. Exposition with his dog Emmy playing The Watson.
- Galileo's Dialogue Concerning The Two Chief World Systems combines the two forms; Salviati (Mr. Exposition) is given both a Watson (Sagredo) and a Straw Loser (Simplicio). The Pope thought Simplicio was a caricature of himself, which was really bad news for Galileo.
- Plato's writings about Socrates are probably the Ur-Example, and certainly the Trope Maker, which means this is Older Than Feudalism.
- This is part of the concept for the Head First books. Even if the speakers happen to be abstract objects.
- Neal Stephenson loves to deliver the Infodump in his novels this way, in Anathem and Cryptonomicon in particular. Anathem even has appendices containing bonus Instructional Dialogue for people who didn't get enough of it in the main text.
- Physicist George Gamow wrote a series of short stories, ostensibly about a man named Mr. Thompson but actually about quantum mechanics and relativity. Half of them are instructional dialogues where Mr. Thompson is playing The Watson to a Mr. Exposition generally referred to only as the Professor; the other half are Mr. Thompson's dreams about what would happen if the physics described in the dialogues was noticeable on a human scale.
- Flatterland by Ian Stewart in large part is a series of dialogues between Victoria Line (The Watson) and the Space Hopper (Mr. Exposition) about various forms of geometry. It helps that they're traveling through all the geometric spaces that the Space Hopper is trying to explain...
- Most of Sophie's World is taken up by a dialogue that summarizes the entirety of Western philosophy from the Pre-Socratics to Sartre.
- Philosophy in the Bedroom, by Maquis de Sade, is both a instructional dialogue on his brand of libertarianism and hard core porn.
- Oscar Wilde's essay "The Portrait of Mr. W. H." is constructed as a lengthy conversation between an older scholar and his younger disciple, to whom he is explaining his theory on the real object of William Shakespeare's romantic sonnets.
- Xanthippic Dialogues is a bunch of instructional dialogues on, mostly, philosophy of dialogue (as in ethics, not rhetoric). It also pretends to be a lost text from V century b.c. and is quite funny.
- The classic geometry video "Turning A Sphere Inside Out" is narrated like this.