That's something I've always wondered and never could find out.

He was one pretty horse though.

This thread has an explanation of 2 ways - one being peanut butter and the other using nylon string.

It may have been a use of both I suspect.

http://www.sitcomsonline.com/boards/showthread.php?s=&threadid=33113&highlight=peanut+butter

I don't believe the peanut butter thing at all. I mean, why would he have moved his mouth right on cue?? Besides, you can even see a string in some episodes...

You mean, he didn't really talk!!! :D

I read a report where Allan Young told how it was done. Before a scene, Mr. Ed's trainer, Les Hylton, used a substance that looked like Peanut Butter and put a wad of it between Mr. Ed's cheek and gums. Though the substance was harmless, Mr. Ed got rid of it by working his lips. While he was moving his lips to get rid of the peanut butter looking substance, the voice of Mr. Ed, Rocky Lane ,did the dialogue. To get him to stop moving his lips, a riding crop was placed against his fore leg and that was the signal for Mr. Ed to keep his mouth closed.

I have been watching the show. I get a few laughs.
Saw it years ago and it was funny then. I don't think the public
would buy it today. The gimmick shows are out. There was a
ton of gimmick shows in the 60's.

Did Mister Ed Receive Electric Shocks to Make the Horse Look Like He Was Talking? (http://legendsrevealed.com/entertainment/2016/09/06/did-mister-ed-receive-electric-shocks-to-make-the-horse-look-like-he-was-talking/)

In my Mr Ed book they mention that one method was that Ed was trained to move his lips when the trainer rubbed/scratched one of his front hoof(s)

What would the ASPCA or Betty White do about this technique?
Could it even be done this way today?

On the subject of "talking" animals, how was Flipper trained to respond on cue?

Alan Young would claim that the old palomino actually called 'Bamboo Harvester' disliked him a great deal- and I wouldn't be surprised if Mr. Ed early on associated seeing the leading man approaching him with folks going to work messing with his mouth so he could 'talk'. He may have long since learned to have accepted if not liked having a metal bit which most working horses have but wires and peanut but were a somewhat late addition to his training.

On the subject of "talking" animals, how was Flipper trained to respond on cue?

When you photograph animals for "purpose" ....you shoot hundreds of pictures for the one or two that you can use.

A food reward helps a lot, but still the animal only cooperates when it feels like it.

It had to be special effects....... I have wondered this also!

[QUOTE=

A food reward helps a lot, but still the animal only cooperates when it feels like it.[/QUOTE]

Same with my "X" lol