The first appearance of a minifig scale horse was a brick built version in the Yellow Castle. Eventually a multi-part molded horse was created that allowed a rider to sit inside a cavity on the back which could be filled by bricks or a saddle element.
In 2012 a new minifig scale horse was introduced as part of the new Lord of the Rings sets. This new version was basically the same size but it had more moving parts allowing the horse to rear up on its hind legs. The head was also significantly modified to produce a more realistic shape. This was met with some objections amongst fans as headpieces produced for the old horses will not fit the new.
- A brief history of LEGO horses on Brickset