Allan Lane, who provided the voice of Mister Ed, originally didn't want his name listed in the credits. So Mister Ed was listed as himself. When the show became a hit, Lane changed his mind. However, the producers wanted to keep the mystique about the talking horse going, so they never put his name in the credits. To appease Lane, the producers increased his salary instead.
Alan Young originally claimed that they made Mister Ed talk using Peanut Butter. However, he later revealed that they made him talk by having the horse chew on a nylon.
Ed tells Wilbur that the reason he is the first person to hear him talk is because he never wanted to talk to anyone else before.
Although a bit confusing, the death of Larry Keating (Addison) forced the series to adjust right in the middle of its broadcast run. Keating passed away on August 28, 1963 during early production (as was practice then more than today) of Season #4 episodes. Keating appears in episodes 1, 2 & 4. Episode 4 was filmed a week before he died at UCLA Medical Center. He was written out of Episode 3 due to illness. Keating had been ill some during Season #3 (1962-1963) and was said to have only missed one episode for the season. However, his health worsened during the summer 1963 hiatus, and there was concern about his returning. Rather than dump him from the series, George Burns who 'owned' Mr. Ed, left his long time friend on contract and did not execute the termination clause until it had run its course in 1964. Burns was very upset when Keating died, and even authorized using his voice over for the ending credits 'This has been a Filmways Production' (before his death 'Mrs. Post' Actress Connie Hines did the voicing) until the series ended and earning his estate small residuals over the years. Young was given a piece of the series from Burns, sources believed he did the same to entice Keating to return to broadcast TV as Addison. Exactly a year later, Burns's wife of 38 years, Gracie Allen, died from heart disease at 69 years old.