Mr. Ed comes out of the closet

Mr Ed, the talking horse, was actually a...trained female zebra named Amelia.

according to Snopes:
During the filming of the pilot episode, production costs mounted as the recalcitrant horse cast as Mister Ed refused to perform on cue ...

The producers of the show were ready to throw in the towel and write off the venture when one of the putative Mister Ed's trainers came up with a solution: the nearby Jungleland animal park in Thousand Oaks, California, had a trained Grevy's zebra that was being used in live shows for the park's daily tour visitors. The zebra (a female, called "Amelia" by its Jungleland handlers) was trained to perform many of the same actions (e.g., opening and closing its mouth, stamping its feet on cue) required in the Mr. Ed role, and Jungleland consented to lend her out for a few days' filming.

Amelia worked out fantastically well, exceeding everyone's expectations, and the pilot was quickly wrapped up and sold to the syndication market. The producers made a generous donation to Jungleland in exchange for continued use of Amelia, and she appeared in all the syndicated episodes as well as all the shows comprising the series' entire five-year run on CBS.

(headsup theJawas)