Knothe has been active in dubbing since the 1970s, most notably as the Polish voice of Daffy Duck. He lent his voice to David Tomlinson in Mary Poppins, Peter Cushing in Star Wars, Jonathan Pryce in The Age of Innocence, Barry Humphries in Immortal Beloved, George Hamilton in Casper Meets Wendy, and Jim Broadbent in The Legend of Tarzan. Cartoon roles, in addition to Daffy, include Spike the bulldog and others in the Tom and Jerry shorts, Magilla Gorilla, various characters in several Scooby-Doo series, Alfred Pennyworth on Batman: The Animated Series and other shows, and Major Talbot on The Incredible Hulk. For animated features, he dubbed Mr. Nebercracker in Monster House and Kai in Frozen.