There are horses! Most notably in the medieval fantasy level, where they are involved with an objective. Also, there is a character called Ponyhawk who is, as can be assumed, part pony.

There is no horse.

There are no horse-related snax.

There is no horse.

There is no horse. There is a rat.

There is no horse, aside from objects (Rocking horses/hobby horse). But, a horse would fit the gameplay very well.

There is no horse.

There is horse iconography (Statues/movie props), but no physical horse.

There is no horse.

Horses are present throughout the game and sometimes even part of the puzzles.