In an interview with Alan Young, he said he had dark blonde hair in real life. On black and white film his hair color blended into the color of Mister Ed too much. The makeup man had Connie Hines hairdresser dye his hair dark so he would stand out. After the show ended Alan let his hair go back to its natural color.
Ed's stunt double Pumpkin was a quarter horse but looked very much like Ed, except for a gold spot in the middle of his white blaze. This spot was covered with white makeup when he worked as Ed's replacement.
Both Arthur Lubin, Mister Ed's producer and most frequent director, and series co-star Larry Keating, had previously been involved in another franchise starring a talking equine, the Francis the Talking Mule film series. Keating appeared in Francis Goes to the Races (1951); Lubin directed this and five other Francis films.
"Mister Ed" was produced, initially, by George Burns McCadden Productions. Burns later said that he hired Alan Young for the part of Wilbur Post because he "just seemed like the sort of guy a horse would talk to."
CBS refused to put the production on their network in its initial premiere in 1960, so the Studebaker Company purchased Mr. Ed and put it into syndication. It was an instant hit, and CBS bought it a year later.
AP News item, 4/22/63: Television's talking horse Mister Ed and Walt Disney's canine film star Big Red won Patsy awards as top animal performers of 1962. The awards were presented Saturday by the American Humane Society.
The lyrics to the famous theme song ("A horse is a horse, of course, of course ...") played over the opening and closing credits were introduced in episode 8 of the first season. The first seven episodes used only an instrumental version of the song.
According to Snopes.com (Lost Legends - Horse of a Different Color) the animal appearing as a horse was actually a trained female Grevy's zebra called "Amelia." The horse that was originally chosen to be "Mr. Ed" was stubborn and refused to perform on cue. Amelia was a trained animal from the nearby Jungleland animal park in Thousand Oaks, California. Since the series was filmed in black and white, the viewing audience couldn't tell the difference. Zebras are smaller than horses, so the set used for Mister Ed's stable was constructed using forced perspective to make the zebra appear larger. This also helped to hide the fact that Alan Young, the series' star, was only 5'4" tall. Since the gait of a zebra and a horse are considerably different, when Mr. Ed was shown walking or running, usually in a long shot, the horse was used.
Mr. Ed was a HORSE, not a Zebra. The Snopes article saying he was a zebra is in their The Lost Legends section which is a joke section "confirming" the really odd or silly stories out there, such as Mr. Ed being a zebra. As Snopes said: We created The Repository of Lost Legends (TRoLL for short) for those of you who don't let the truth get in the way of a good story.