Taraxippus is one of Equestria's many boogeyponies, though one whose name has fallen out of favor in the last few centuries. Parents of unruly children who wouldn't eat their alfalfa would tell stories of Taraxippus, who comes in the night to give wayward, hungry foals such a fright, they'd eat their own leg, or their brother, or their parents. And then where would they be? (One can see why Celestia preferred to phase the legends out of the common myths.)
But, like so many mythical creatures of Equestria, the Pony-Frightener is real, a ghostly minotaur with a visage so terrifying, few remember their encounters with him. Why, when young Princess Twilight Sparkle met him, she was scared out of her...
No, wait, that's not what it says. Apparently, after an initial startle when he snuck up on her in her castle's library, she was completely nonplussed by his appearance. Baffled, the spirit asked her why she wasn't afraid of being forced to eat another pony, to which she replied, "I've had lunches at the CHS cafeteria. Do you have any idea what they serve in those burgers? Because I sure don't."
Taraxippus has not been sighted in Equestria for quite some time since.