Edward Askew Sothern the play that Abraham Lincoln was watching when he was assassinated. Sothern's role was Lord Dundreary, a caricature of a brainless English nobleman. At first, he was reluctant to accept the role; it was so small and unimportant that he felt it beneath him and feared it might damage his reputation. He mentioned his qualms to his friend, Joseph Jefferson, who had been cast in the leading role of Asa Trenchard in the play. Jefferson supposedly responded with the famous line: "There are no small parts, only small actors." On 15 October 1858, "Our American Cousin" premiered in New York.
What Was Missing seen by 0.4 percent of all households aged 18 to 49 years old were watching television at the time of the episodes' airing. Tyler Foster of DVD Talk called the episode a "highlight" of the "Fionna & Cake" DVD. Specifically, he praised the song "I'm Just Your Problem", calling it both a "fan favorite" and "significant as the moment I decided I was a fan". Dana Piccoli of AfterEllen.com enjoyed the way the episode "alluded to perhaps, more than platonic feelings between" Princess Bubblegum and Marceline, as well as the fact that "What Was Missing" was underlined by potential lesbian