The cartoon, loosely based on Mark Twain's A Connecticut Yankee in King Arthur's Court, begins with Bugs Bunny reading a book on the Knights of the Round Table. While reading, an apple hits his head and he finds himself in the times of King Arthur. When he wakes up he finds himself at the pointy end of a knight's lance. Bugs asks him, "What's up, Duke?" and the knight commands Bugs to surrender as prisoner of his lance. The knight identifies himself as "Sir O of Kay, Earl of Watercress, Sir Osis of The Liver, Knight of the Garter, and Baron of Wooster-cester-shister-shyster-schuster-shister-sister-shire...sher." Ready to take Bugs' challenge to tilt with him for the insult of Bugs' friends Duke of Ellington, Count of Basie, Earl of Hines, Cab of Calloway and Satchmo of Armstrong, who are called "upstarts and rogues" by the knight (whom Bugs calls "Pressure Cooker" and "Sir Rupp of Figgs") offers Bugs a too-heavy sword, then begins to charge at him, during several comedic attempts by Bugs to get the sword off the ground. At the last second, Bugs puts his leg out tripping the knight's horse. The horse falls and the knight pole vaults on his lance over the castle wall and into a high window of a castle tower, falling LOUDLY to the bottom inside the tower.
Bugs is later chased by a dragon who breaths fire at him. He later stops it by spraying water into the dragon's mouth. The dragon loses its fire breath and runs away.
Bugs later goes to another castle, the residence of a warlock named Merlin of Monroe (an obvious reference to Marilyn Monroe). He later tricks the warlock into becoming a donkey. To try to return to the present, Bugs Bunny throws an apple in the air to hit him on the head ("Well, why not? After all, they laughed at the man when he discovered penicillin"). He later wakes up and walks down a country road, thinking it was just a dream...until he hears a farmer call a donkey "Merlin".