He is particularly notable for his performance as the voice of the Caterpillar in the 1951 Disney animated adaptation of "Alice in Wonderland", and for his small role of Herr Falkstein in the 1974 Mel Brooks comedy "Young Frankenstein". Haydn was memorable as the manservant Rogers in the 1945 adaptation of Agatha Christie's "And Then There Were None". He is well remembered for his role as William Brown in the 1962 version of "Mutiny on the Bounty". Perhaps his most acclaimed role was in Rodgers and Hammerstein's 1965 film musical "The Sound of Music", in which he played the Von Trapps' family friend Max Detweiler.