I have an Adult sized Unicorn for Adults, Elders, and Teens with 2 ride gaits, it also will graze, eat and play a light whinney sound.
The pony sized unicorn is for children it has only one ride option with the graze, eat and a pet option.
The unicorn has to be placed heading north, for the Sims to ride it correctly. That is north from where the lots sits within the neighborhood.
Body skill and fitness is gained when sims ride either of these unicorns.
Both items are found under Knowledge/Exercise Equipment.
Thanks to Rougue for the texture, and Shaklin for her original rideable item.
Video for pony is posted here:
Video for Unicorn is posted here: