Horace is given to Salad Fingers by Jeremy Fisher, strangely enough with arms. He accepts the gift happily and shortly after eats Jeremy Fisher and quickly forgets. He then starts playing with Horace making strange horse sounds. Horace then "accompanies" Salad Fingers on his visit to the toilet outside the house. After a short argument with the toilet, in which only he talks, Salad Fingers asks Horace to take him home, seemingly scared.
Apparently he puts him by a mirror when he is not playing with him (as seen in episode 10).
In episode 10 he is seen alive in the woods in actual horse size, being ripped apart by Dr. Papanak. Salad Fingers seems concerned at first, but then smiles and tells him: "I know it hurts, but try and sit still whilst the doctor eats your blood.", Horace sheds a tear. He shows up at the house afterwards, apparently stitched up. Salad Fingers gets annoyed because there are a lot of other horses, and he told Horace he could bring "one friend only".After finding the skeleton of Milford Cubicle, Salad fingers blames the horses, calling them "foul creatures", and removes them from his house, along with Horace.
Horace Horsecollar is a spotted horse. In his toy state, he doesn't move by himself, and is potentially made out of plastic, as seen by his rigid shape. In his alive state, he is able to move by himself, and shed tears. He's white with black spots, and his main characteristic are his deep black eyes with bright-red outline. His tail is yellowish, and the lower half of his legs are white and green. He's got a long stitch on the left side of his body, probably after being patched up by Dr. Papanak.