Tuffnut Thorston

Tuffnut Thorston is a teenage member of the Hairy Hooligan tribe in the book. He is the fraternal Twin of Ruffnut Thorston in the movie franchise and they are constantly arguing with each other, often to the point of physical violence, though never seriously enough to separate them for too long.

Personality
Although never said throughout the show, Tuffnut seems to be slightly more dominant twin than his sister and has a more prominent role, especially in the TV Series. Together, he and his sister love to get into trouble, even if it means getting scolded by the chief of the village. Tuff likes the idea of Ruff being in danger (as he stated that when Ruff was on fire one time, he just watched for a while before he decided to help put her out). Tuff enjoys the chance to argue and wrestle with his sister, although it usually ends with Ruff overpowering him, either verbally or physically. He shares many similar traits with his sister. The only thing that seems to be apparent in difference, is he enjoys gross things as opposed to his sister (as seen in Gift of the Night Fury). Despite having a close sibling relationship, Tuff is frustrated when he has to share everything with his sister, but he's willing to make amends with Ruff to save his dragon. Although sharing rivalry with his sister, on occasion, he will help her if she is in trouble. He often thinks highly of his own skills, claiming that he was the world's deadliest weapon. In the TV series, Tuff appears to show a thrill-seeking and masochistic personality, displaying an attraction to dangerous situations and seems to enjoy or looks forward too whatever bodily harm he receives (usually by his sister).

Ruffnut
Ruffnut and Tuffnut have a strong love/hate sibling relationship. Although most of the time quarreling and fighting over trivial things in life, they show an inseparable bond with each other and rarely spend too much time apart. They both enjoy the feeling of pain, especially if the pain is inflicted on the other twin. Tuffnut in particular has even stated that he had merely watched Ruff when she was caught on fire once before deciding to help her.

On occasion, Tuffnut is willing to help his sister. Tuff showed concern for her, asking her to leave Scauldy behind when the Changewings were approaching and was happily riding Belch afterwards, watching his sister who was safe, despite the sacrifice she made for Scauldy to make. After she says good-bye to Scauldy she starts to feel sad, but Tuff quickly teases her about her looking like a boy, in which Tuff succeeds in making Ruff smile again.

As twins, Tuffnut and Ruffnut share a strong invisible connection towards each other. They have the ability to understand each others thoughts and ideas without speaking, as shown several times to finish each others sentences or to have the same idea at the same time. They also have the ability to stay together as they are rarely too far apart for a long time. Wherever one twin goes, the other twin is never far behind, even if they intentionally try to stay away from each other. Ruff and Tuff also work incredibly well together (when they want to) and can synchronize themselves to do the same actions at the same time. It's also possible that they are able to sense where the other is and what happened to them, as other twins are able to do.

Barf and Belch
Being their dragon, the twins had to share riding it. The twins care tremendously about their dragon, although not as much as Hiccup. One head is loyal to each twin (Barf and Ruff, Belch and Tuff) and on occasion, the heads will fight each other when the twins fight each other. Usually the heads will work in unity if they feel that their riders are in danger and feel that their rider's constant quarreling is annoying. Both dragon and rider are willing to risk their necks to save each other. Tuff even states that Barf and Belch is his "totally awesome dragon" that he shares with his "totally un-awesome sister". Several times during the TV Series, Barf and Belch are seen to be extremely protective of their riders when they are in danger, as shown as they are willing to fight a several Enemies, such as a wild Typhoomerang and Scauldron, to defend Tuffnut in Zippleback Down and Ruffnut in Free Scauldy, as well as leaving the cave in The Night and the Fury to search for Ruff.

Hiccup Haddock
Not a lot of screen time is shown between the twins and Hiccup. Most of the time, they follow Hiccup's commands, although not always done in the right way. On occasion, they disobey him or misinterpret his orders. Despite Hiccup doubting their abilities most of the time, he acknowledges their abilities to work together if they want to. He gains respect for the twins when they figure out the idea to "fight fire with fire" in "Zippleback Down" and Tuffnut's ability to train Torch. Although finding them annoying from time-to-time, Hiccup is shown to care for them as he and the other Viking Teens attempt to find them after their disappearance in "View To A Skrill Part II" and was relieved to find out that Ruff and Tuff were both okay. He also acknowledges their decision to follow Alvin's ship to spy on him. They also care about Hiccup, (even though it's hard to tell), like when they, along with the other riders, were very happy to see that he was alive after the battle with the Red Death and when he fell down a hole, (then came out okay later), in Portrait of Hiccup as a Buff Young Man.

Astrid Hofferson
Although they rarely interact in the show or movie, they remain neutral to each other and will work together when it comes to it. Most times, Astrid will get angry if they do something wrong, especially if it's because they're not paying attention or just being silly. Like Hiccup, she doubts their abilities as Dragon Trainers due to their inability to pay attention, although it is assumed that she gained respect towards the twins when they put out the fire and trained Torch. On occasion, she will punch Tuff if he angers her, although Astrid is never shown on-screen to hit Ruffnut. Astrid was one of the Vikings who attempted to find the twins after they were blasted out of the sky in "A View to a Skrill Part II". It is presumed that off-screen, she had attempted to find them although Stormfly soon grew exhausted, showing that she does indeed care for the twins.

Snotlout Jorgenson
Snotlout and the twins share a close relationship. Often times, the twins will follow Snotlout and act as one of his supporters when he bullies Hiccup and possibly Fishlegs as well in the first film. In the game, they listen to Snotlout's plan to cheat in the competition against Hiccup/Astrid. Snotlout often thinks the twins are incredibly dumb and in return, they sometimes exclude Snotlout from their ideas, as seen in "Fright of Passage". Although sometimes siding with Snotlout, they occasionally bully him back, like how they fooled him into thinking he was dying in "The Flight Stuff". In View to a Skrill, it's presumed that Snotlout had attempted to find the twins (as stated by Hiccup) after they disappeared after being blasted out of the sky, which shows his apparent caring personality towards them.

Fishlegs Ingerman
Fishlegs and the twins rarely show any screen time together. Sometimes, the twins are seen to bully Fishlegs because of his size, although Fishlegs bests the twins in terms of knowledge. The twins, particularly Tuff, find it annoying that Fishlegs knows a lot of things. In View to a Skrill Part II, Fishlegs attempted to find the twins after they were blasted out of the sky, along with Meatlug, but ends up over-exhausting his dragon. Even so, he offered to join Hiccup on his search again and shows worry when Hiccup tells him that there was no sign of them.

Stoick the Vast
Stoick is well aware that the twins are capable of causing dangerous accidents and pranks, as well as notorious for causing mischief. Ruff and Tuff show a level of respect for Stoick, possibly because he's Hiccup's dad, but also like to make fun of him when he's not around. He's the one who possibly created the saying "Where there's a smoke, there's the twins".