Elliott Gould was the original voice of the horse. After a poor test screening of the film, the horse's half of the script was rewritten by Andy Breckman in an effort to make the film funnier. John Candy was hired to re-record the horse's voice. He ignored the new script and improvised the dialogue instead.
Reportedly, when Bobcat Goldthwait was given a script of the movie, he wrote "Why would I do this?" on the cover. His agent responded by drawing a dollar sign over it.
After Pee-wee's Big Adventure (1985), Tim Burton was offered to direct, but declined. Burton felt the script was so poor and unimaginative that he felt somewhat insulted by the idea that he would be interested in doing it.
Virginia Madsen said she made this movie for the money, and so her sister's children could see it. She admits the movie was an embarrassment, but she needed the money at the time, and she was not ashamed to take the role.
According to Bobcat Goldthwait, when he was a guest on Gilbert Gottfried's Amazing Colossal Podcast, the crew got the horse to "talk" by hitting it in the face with a stick right before a take.