Unimpressed with him in tights, the producers made Danny Kaye wear "leg falsies" to improve the shape of his legs. This adds a touch of irony when Hubert Hawkins offers the Princess all of him, including his legs and calves.
Danny Kaye's daughter, Dena Kaye, said for the rest of his life, when people recognized Danny in a restaurant, they would walk up and spout the entire "brew that is true" speech.
Basil Rathbone was a world-class fencer and it was due to his efforts that the hilarious fencing scene was filmed without injury. He later admitted that several times he was almost skewered by Danny Kaye's sword. In fact, Kaye at one point flicked Rathbone's wig off his head with the epee, drawing blood on the top of his scalp.
During the "Maladjusted Jester" sequence, King Roderick I (Cecil Parker) kicks Hawkins (Danny Kaye) every time he makes a mistake. It took 11 takes, and afterward, Kaye said he had bruises all over his hip.