For decades, film critics and historians have theorized that because Dumont never broke character or smiled at Groucho's jokes, she did not "get" the Marxes' humor. On the contrary, Dumont, a seasoned stage professional, maintained her "straight" appearance to enhance the Marxes' comedy. In 1965, shortly before Dumont's death, The Hollywood Palace featured a recreation of "Hooray for Captain Spaulding" (from the Marxes' 1930 film Animal Crackers) in which Dumont can be seen laughing at Groucho's ad-libs — proving that she got the jokes.
On February 26, 1965, eight days before her death, Dumont made her final acting appearance on the television program The Hollywood Palace, where she was reunited with Groucho, the week's guest host. They performed material from Captain Spaulding's introductory scene in Animal Crackers, including the song "Hooray for Captain Spaulding". The taped show was broadcast on April 17, 1965.
Moeller died during the 1918 influenza pandemic, after which Dumont reluctantly returned to the Broadway stage. She never remarried, and died from a heart attack on March 6, 1965. She was cremated and her ashes were interred in the vault at the Chapel of the Pines Crematory in Los Angeles. She was 82, although many obituaries erroneously gave her age as 75.