When Mr. Ed was tired of working, he'd just walk off the set.
The horse wouldn't respond to any of his co-stars, just his trainer, Lester Hilton. This meant that Hilton had to be on the set at all times, calling out commands or giving them with hand signals.
This was one of the few television series to start in syndication, then be picked up by a major network.
In an interview with Alan Young, he said he had dark blond hair in real life. On black-and-white film, his hair color blended into the color of Mr. Ed too much. The make-up artist had Connie Hines' hairdresser dye his hair dark so he would stand out. After the show ended, Young let his hair go back to its natural color.