Possible Clues:

• Loquacious equine of '60s TV
• TV character voiced by Rocky Lane
• Steed who could read
• Horse show
• He'll 'talk 'til his voice is hoarse'
• Stable character of old TV
• Black-and-white horse?
• Show horse
• "What kind of a name is 'Wilbur' for a man?" speaker
• Stable role on TV?