Possible Clues:

• Subject of the lyric 'A horse is a horse, of course, of course'
• Comical equine
• Equine star
• TV talking horse
• Horse in a 60's sitcom
• Bamboo Harvester “played” him
• Equine quipster
• "Famous" talker of '60s TV
• Chatty equine
• 60's lip-syncher