While Bugs reads a book on the Knights of the Round Table, an apple hits his head and knocks him out. When he wakes up he finds himself in the times of King Arthur, at the pointy end of a knight's lance. Bugs asks, "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 him by spraying water into the dragon's mouth. The dragon loses his fire breath, whimpers about it, and runs away.
Bugs later goes to another castle, the residence of a warlock named Merlin of Monroe (a reference to Marilyn Monroe). He later tricks the warlock into becoming a donkey. Angered by this, Merlin tries to change himself back to normal by also unzipping, but is shocked when he realizes that he is in the same donkey appearance, then tries to unzip again, feels confused, and ends up being in the same donkey appearance, no matter how many times he unzips the costume. 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".
- The cartoon is loosely based on Mark Twain's A Connecticut Yankee in King Arthur's Court.
- Much of this cartoon's plot was utilized in the PlayStation 1 video game, Bugs Bunny: Lost in Time, down to reenacting the scenes with Merlin shot for shot for the opening and ending cut scenes.
Versions of this cartoon shown on Cartoon Network and Boomerang cut the short scene of Bugs Bunny tying a blindfold over his eyes as the knight charges into him and the brief scene of Bugs still standing as the knight charges into him before Bugs sticks his foot out and makes the horse trip and the knight fly off his horse and into the tower. These cuts were done because Bugs had a lit cigarette in his mouth and Cartoon Network (and, by proxy, Boomerang) almost always cuts cigarette smoking from their classic cartoons.
- VHS - Looney Tunes: The Collectors Edition, Vol. 11: Wabbit Tales
- VHS - Bugs Bunny's Hare-Raising Tales
- DVD - Looney Tunes Golden Collection: Volume 4, Disc 1
Knight-Mare Hare on the SFX Resource