|“|| The Hideous Zippleback known as Barf and Belch is a two-headed dragon that constantly bickers with itself. Perhaps it is this trait that got the attention of the highly aggressive twins, Ruffnut and Tuffnut. These siblings may care for each other, but they also have a habit of fighting amongst themselves.|
While they were initially enemies during Ruffnut’s and Tuffnut’s time in dragon school, both the riders and the dragon seem to work best when they come together as a united front. This first became evident after the battle against the Red Death, in which both Ruffnut and Tuffnut learned to command their respective dragon heads. Now, the four of them have formed a strong bond. Ruffnut prefers to ride on Barf and Tuffnut tends to ride on Belch. When all four of them are working as a team, enemies had better watch out!
|— School of Dragons Game Guide|
Ruffnut and Tuffnut share a Hideous Zippleback dragon they named Barf and Belch. The bond between dragon and rider started in the first movie, How to Train Your Dragon, when Hiccup introduced the dragons to their new riders. They've been inseparable since.
Not much scenes are shown in this film about the bond of the twins and their dragon, simply because it was already close to the end of the film that they started the bond with each other, although on the scenes of the war between the riders and the Red Death, the twins are scene to already have a playful (and at some times, annoying) attitude that goes the same with their dragon. But because the twins don't always agree with each other, this has also caused some problems with the dragon as well.
There aren't that many scenes that are shown to improve the relationship of the twins and their dragon but at one part of the short film, all the dragons in Berk left and went to the Berkery. The twins were saddened (like everybody else) that they couldn't spend Snoggletog with their beloved dragon and are also seen to be jealous of Hiccup because his dragon, Toothless, can't go anywhere without him.
In the episode, "Animal House", Barf and Belch displays a protective instinct to his Riders, as well as other Vikings and animals in the Berk community.
In "In Dragons We Trust", Barf and Belch as well as the other dragons are framed for destruction around the village. Stoick banishes the dragons to Dragon Island. The Twins and their dragon display sadness at their parting, each rider and each dragon head exchanging hugs. Despite the favoritism each Twin demonstrates for the head they ride, they are still saddened to see all of Barf and Belch go.
In Race to the Edge, although the twins can still be seen causing mayhem and random destruction along with their dragon, throughout the whole show, in battle, they work together as a team and defeat their enemies with some tricks up their sleeves.
In "The Zippleback Experience", Barf and Belch decided to stick with Hiccup and Toothless to serve them until their life debt by abandoning their riders, Ruff and Tuff. On account of this, the twins get very upset and even argued over who drove their dragon away, as well as tried to perform numerous attempts - whether it's dangerous or not - in order to get their dragon back. When everyone rushed to their dragons and took to the air as soon as they saw Barf and Belch's distress signal, Ruff and Tuff weren't willing to get left behind. Fortunately, they noticed that Toothless was beside them. The twins did not hesitate to hitch a ride on Toothless to help aid the rescue of their dragon, including Hiccup.
The riders have surely improved their relationship with their dragon over the years. Their first scene together is the part where the all the riders (except Hiccup) are seen to be competing against each other in Dragon Racing. Barf and Belch listen to their riders and follow their commands and vice versa. It is also seen in this film that the twins may be sharing a dragon, but at sometimes, they just can't get along, and their dragon has to put up with that as well.
Another scene is how sad and sorrowed the twins are (and everybody else for that matter) when their dragon was controlled by Drago's Alpha, and had no choice but to leave their sides. This shows that their relationship is as strong as any Dragon/Rider bond there is, no matter how they don't show it.
Tuffnut and Ruffnut both favor the head they ride on as shown when they are reunited with Barf and Belch after Toothless becomes the new alpha. Ruffnut shoves Barf away in favour of hugging Belch, while Tuffnut is shown hugging Barf in preference over Belch.