Barf and Belch

"What we can't get you is another Barf and Belch" - Hiccup to the twins, Twinsanity.

Barf and Belch is the male Hideous Zippleback owned and trained by Ruffnut and Tuffnut. Barf and Belch are like their owners, they have trouble deciding which head goes what direction and focusing on one target. However, unlike Ruffnut and Tuffnut, they can work together and find their owners annoying with their constant bickering.

Personality
Barf and Belch have the personality of a normal Zippleback; however, they have a laughable sense of humor. They enjoy doing the tasks Ruffnut and Tuffnut tell them to do, but they are in constant quarrel because of the fact that they sometimes have to listen to two different commands they are unable to do. Despite this, they usually help the Twins with their pranks. Barf and Belch often get annoyed with their riders constant bickering- which once led to them going wandering around Berk after the twins started issuing contradictory commands to each head- but both are willing to protect their riders at any costs. For example, when Torch first approached Tuffnut as an adult, although the dragon only stayed because Belch didn't want to leave him, both were willing to fight what appeared to be a wild Typhoomerang in order to protect him (Zippleback Down) and they left the cave that they were supposed to stay in during Astrid's harsh training session to find Ruffnut who they felt was in danger (The Night and the Fury). They are very in sync with their riders, mimicking several actions of them, such as their 'high-fives' (headbutting each other). They have also been seen fighting at the same time as their Riders are bickering.

Appearance
Barf and Belch have the appearance of a normal Zippleback. Despite the head's resemblance towards each other, there are minor differences that each head has. Barf has a slightly curved horn as opposed to Belch's horn which is straighter. Barf's longest teeth are in the back of his jaw and Belch has his longest teeth in front of his jaw. Barf's skin is also slightly more lighter than Belch's. The skin color and tooth differences disappear by the time of the second movie (from what has been seen in images, this is most likely a production goof). Barf and Belch are 66ft long, have a 38ft wingspan and weight about 6,036 lbs.

In How to Train Your Dragon
Barf and Belch were one of the captured dragons used to train the Viking Teens. The lesson they taught was to work together to find the head that lit up the gas (which was Belch). Later, Hiccup manages to get Ruffnut and Tuffnut to bond with them in time to help defeat the Red Death.

At the climax of the film, Ruffnut and Tuffnut, along with the rest of the Viking's teens, were on dragons. They helped the twins distract the Red Death to allow Snotlout and Fishlegs to attack them. By the end of the movie, the twins are seen riding Barf and Belch along with the other Viking Teens.

In Dragons: Riders of Berk
It was revealed in the show that the left head's name is Barf and the right is Belch, with Ruffnut commanding Barf while Tuffnut controls Belch.

In the episode In Dragons We Trust, Barf and Belch are framed by Mildew of the crime of stealing all the boots of the village during "boot night," sleeping in a bed of boots. They are then proven innocent by the comparison of their tracks and the tracks at the scene, noting how their tracks are deeper.

In Twinsanity, Barf and Belch briefly went rogue after Ruffnut and Tuffnut's conflict with each other reached a point where they were issuing contradictory orders to the head they controlled. The Zippleback was roaming around the village just as renegade Viking chief Dagur the Deranged arrived to discuss a treaty. Wishing to sign the treaty in dragon's blood, Dagur captured and nearly decapitated Barf and Belch, but the twins were able to reconcile in time to help their dragon escape, with the other dragons faking an attack on the training ring to conceal Berk's newly trained dragons in order to avoid provoking war.

In Dragons: Defenders of Berk
Barf and Belch appear in almost every episode, appearing alongside or being ridden by the twins.

In the episode, Zippleback Down, they accompany the twins as they attempt to dislodge hidden traps. When Tuffnut is captured, they are ordered by Ruffnut to watch over her brother while she attempts to go get Hiccup so he can free her brother. Although annoyed by Tuffnut's constant efforts to start a conversation with them, they end up playing with him (though Tuffnut didn't enjoy it much). They try to protect Tuffnut when a wild Typhoomerang (Torch) aggressively approaches him. Defending Tuffnut, they are caught in a bola-string trap, but they manage to cause a big enough explosion to start a forest fire somewhere off. They are freed by Hiccup when he arrives on Toothless and they ride Torch. The Zippleback end up helping to put out the forest fire and arrive back home on Berk safely on Torch's back. Later that night, when Ruffnut fails to free her brother from the trap and ends up with both of them being trapped, they leave their riders to bicker to presumably return home.

In A View to a Skrill Part I and Part II, Barf and Belch help to free the Skrill from the ice block, along with Snotlout and Hookfang. The twins ride them and they help to snuff out the Skrill from the clouds so Hiccup can knock it down. They manage to save Hiccup from being blasted by lightning, although the twins and them end up being chased themselves. Barf and Belch manage to land safely on an outcroping of land in the middle of the ocean and help the twins go after Alvin when they see him collecting the Skrill. Later they are seen on Outcast Island being watched over by Ruffnut as Tuffnut and Hiccup try to gather information about the Outcast/Berserker alliance. They appear again later to help Toothless seal up the hole, trapping the Skrill in ice once again.

How to Train Your Dragon 2
Barf and Belch briefly appear being ridden by their riders, Ruffnut and Tuffnut. Barf in particular shows annoyance and slight aggressiveness when Snotlout approaches Ruffnut to flirt with her.

Relationships
Ruffnut and Tuffnut Thorston: They met for the first time in the Arena, where Barf and Belch attacked them just like the other Teens. Later, Hiccup helped the two of them to train Barf and Belch, forging a strong bond between the two. In the TV Series, not many episodes are focused on the relationship between these three. However, it can be assumed they care greatly for one another. In Twinsanity, the Twins were bickering over who Barf and Belch belonged to. When they couldn't get to an agreement, they both decided to stop with anything Dragon or sibling related. However, when the Gang told them Dagur wanted to decipate them in order to get their blood for the treaty, they were determind to save them. In Zippleback Down, Tuffnut claimed Barf and Belch is a 'Totally Awesome Dragon', with he shared with his 'Totally Not-Awesome sister'.

Hookfang: Hookfang and Barf and Belch have been seen fighting several times, though with unknown reasons.

Dagur the Deranged: When Dagur came to the Isle of Berk to sign a peace treaty with Stoick, he claimed they needed Dragon blood in order to sign it. This lead them to hunting Barf and Belch. Though Dagur tried to decapitate them, Barf and Belch escaped and defeated him with the aid of the other Riders and their Dragons. Barf and Belch later assisted Toothless in defeating Dagur's Skrill, trapping it in the ice once again.

Skills and Ablities
Barf and Belch seem to have the normal abilities of a regular Zippleback, although some of their abilities and gain skills are heightened due to training under Ruffnut and Tuffnut.

Strength: Barf and Belch are seen to be able to lift up heavy objects with their claws. Both claws can lift up a weight of two heavy grown adult Vikings. They didn't budge when Toothless tried dragging them off the roof and they can carry heavy Vikings on Their neck, like Fishlegs. This was seen in Twinsanity. Barf and Belch have strong jaws, but can hold back their strength. This is seen when they hold Ruffnut or Tuffnut in their jaws.

Acrobatics: This is seen in the battle against the Red Death, when they manage to avoid sudden bursts of fire. Despite claiming that Zipplebacks are bad fliers, they are surprisingly agile. They have a very flexible body, but they can tangle their neck by accident.

Speed: Barf and Belch have the speed of an average Zippleback, but they were also able to catch up with the Skrill in 'A View to a Skrill Part I', although the Skrill had been slowed down slightly by Stormfly and Toothless.

Gas and Spark: Barf is able to breath a large amount of green gas. This gas confuses and disorients people, with the exception of the Thorston Twins. Belch is able to release an electric spark. When combined, they can make a large explosion.

Stealth: Barf lets out a green, thick gas, wich they use in order to hide. From there, they sneak upon unexspected enemies or prey, attacking them.

Intelligence and Communication Skills: They always know when their riders have gone too far in fighting and often take charge if they are in trouble. But, like their riders, they often fight with one another. Despite having learned hand signals, they occasionally misunderstand it. Like all Academy dragons, including Torch, Barf and Belch are trained in the basics of hand signals. Although, Barf will only obey Ruffnut's hand-signals and Belch will only obey Tuffnut's hand signals.

Endurance and stamina: Endurance and stamina, as was demonstrated several times. They could still get up after being hit by the attacks of the attacks of a Skrill, Night Fury, (A combined attack to be exactly) and Typhoomerang.

Trivia

 * Barf and Belch were originally supposed to be ridden by Fishlegs, and he briefly rode on Barf in Twinsanity after the dragon flew away without the twins, along with Snotlout, who rode on Belch.
 * While the dragon is male, Barf and Belch are commonly referred to as "them" or "it," most likely due to the two heads being individuals. The only episode where they are referred to as "he" is Dragon Flower.
 * So far, Barf and Belch is the only one of the Academy dragons that Hiccup hasn't ridden at least once.
 * Barf and Belch are the only known Zippleback that has riders, this might be because you need two of them, in this case, Ruffnut and Tuffnut.
 * The difference in the color of skin between Barf and Belch is probably a production goof, like the changes in tooth length.
 * In the How to Train Your Dragon Movie, when they were approaching Hiccup, Barf and Belch spread their wings and start hissing, which is similar to the behavior of the Dilophosaurus in the movie, Jurassic Park. Barf and Belch are never seen doing this again.
 * They seem to chase their tails when they are bored.
 * Although Ruffnut and Tuffnut share Barf and Belch, Tuffnut seems to be closer to both heads overall; in "Zippleback Down", when he was briefly trapped with only Barf and Belch for company, Tuffnut expressed regret that he and Barf didn't socialize much, but in How to Train Your Dragon 2 Ruffnut actively shoved Belch away in favour of welcoming Barf back after Toothless defeated Drago's Bewilderbeast.
 * Barf & Belch's full names would be Barf Thorston & Belch Thorston.