A horse is a domesticated animal that is mostly used for transportation.
In mainstream Smurfs media, Sir Johan rides upon a horse named Bayard. Various other characters tend to use horses as their main source of transportation, either saddleback or driving a stage coach, in both the comics and cartoon show.
In another cartoon episode, 'Revenge Of The Smurfs", there are some horses that rampaged through the village as some soldiers are retreating. In the later part of the episode, Smurfette, Hefty, Jokey, and Greedy go to the camp and free the military horses to give a trick to the soldiers who destroyed their village.
In season 6, Nightmare is a horse that appeared in the episodes "Lazy's Nightmare" and "Sleepless Smurfs." It can breathe fire and is the horse of the evil Dream Demon Morphio who uses it for a easy way to chase the Smurfs in the Evil Dreamworld.
In the time-travel episode "Phantom Bagpiper", the Smurfs met two horses, Cassie and Scotty, who belong to Laird Milton McKilty. However, an evil man, Frugal McDougal, steals Scotty from Milton along with some Smurfs. In order to help rescue Scotty, the Smurfs and McDougal decided to have a horse race. Smurfette becomes the jockey of Cassie to match with McDougal. By the end of the story, the Smurfs win and Scotty and the captured Smurfs are returned.