Hope did many specials for the NBC television network in the following decades, beginning in April 1950. He was one of the first people to use cue cards . The shows often were sponsored by General Motors (1955–61), Chrysler (1963–73), and Texaco (1975–85).  Hope's Christmas specials were popular favorites and often featured a performance of " Silver Bells "—from his 1951 film The Lemon Drop Kid —done as a duet with an often much younger female guest star such as Olivia Newton-John , Barbara Eden , and Brooke Shields ,  or with his wife Dolores, a former singer with whom he dueted on two specials. Hope's 1970 and 1971 Christmas specials for NBC—filmed in Vietnam in front of military audiences at the height of the war—are on the list of the Top 46 . network prime-time telecasts . Both were seen by more than 60 percent of the . households watching television.