The two-headed dragon ridden by Ruffnut and Tuffnut in How to Train Your Dragon is named Barf and Belch.
Barf and Belch is a Hideous Zippleback, a dragon species with two heads and two distinct personalities. Ruffnut and Tuffnut each control one side of the dragon, making their riding partnership as argumentative as their relationship with each other.
The names are often treated as if they identify two separate dragons, but Barf and Belch are the two heads of one dragon. Stormfly and Hookfang are separate dragons ridden by Astrid and Snotlout, while Meatlug belongs to Fishlegs. Toothless and the Light Fury are also separate individuals.
The Zippleback’s dual-headed design allows the franchise to turn the twins’ constant disagreements into a visual joke. The dragon’s two heads must coordinate even when its riders are busy competing or arguing.