Michael Palin has a slight speech impediment (saying the "R" sound as a "W") which is noticeable during the Agatha Christie parody. Palin would later use an exaggerated version of this impediment for his portrayal of Pontius Pilate in Life of Brian (1979).
"Jackie Charlton And The Tonettes" is a fictitious band, taking its name from Jack Charlton, one of the stars of the English football squad that won the World Cup title in 1966. In reality "Yummy Yummy Yummy" was recorded by the Ohio Express.