Trivia: Not a mistake, just a fact. Exactly 2,357 pies were used in the big pie fight.
Trivia: At many points in the movie, the music playing in the background are slightly different versions of the song "A Hard Day's Night." This was the title track from the Beatles previous movie.
Trivia: In the beginning of the movie there is a reference to a Frenchman who had crossed the Channel by plane in the previous year (1909). The man meant is Louis Blériot, who flew from Calais to Dover in his famous craft 'Blériot XI' in 37 minutes. Again it was a competition race, for a 1000 Pounds set by the London Daily Mail.
Trivia: When all of the characters are together in Peter O'Toole's hotel room towards the end of the film, Peter Sellers exclaims that Ursula Andress is a "personal friend of James Bond!", in reference to her performance in the first Bond film, Dr. No (1962). This was an ad-lib by Sellers, and Andress visibly cracks up before the shot cuts away.