Ride the Pony is a Rare Fortnite Emote. Ride the Pony was available via the Battle Pass during Season 2 and could be unlocked at Tier 20.
How-to Get the Ride the Pony Emote
Ride the Pony is part of Season 2. If that season is still currently in the game, you can obtain this item by purchasing and/or leveling up your Battle Pass.