AlliesEditmovie, Toothless has grown into his loyalty to Hiccup as he and the boy became more and more familiar with each other. Hiccup later allowed Toothless to fly again, and in doing so he would give the dragon back the thing he held most dear. As the movie progress, Toothless was willing to risk his own life to save his friend, protecting Hiccup from Hookfang and going as far as to dive his entire body into the exploding Red Death in order to save him.
In the fanfiction, authors still keep Hiccup and Toothless' unbreakable bond they share in the film and TV series, as it is an essential part of both of their characters.
Toothless shares a light bond with Merida through Hiccup, and the fact that Merida has an affinity for animals through her own horse. In fanfiction, she is most commonly the one who rides Toothless behind Hiccup.
Toothless has interaction with Rapunzel, but not much. The closest interaction they have would be Rapunzel offering to heal Toothless' tail. With Rapunzel's open and innocent personality, it is likely for Toothless to trust Rapunzel quicker than he would Jack or Merida. Because of Rapunzel's personality towards animals, Toothless does like a few scratches or pats from her. Fans have made it to where their introduction is played for laughs, Rapunzel going into a "cuteness frenzy" over the dragon instead of the more appropriate, fearful reaction others would feel.
Toothless is a powerful creature, however when placed up against Pitch without Hiccup there is not much the Night Fury can do. Pitch's ability to move through shadow means that he can easily out-maneuver the grounded dragon. His control of the nightmare sand means that he could force Toothless to do battle with his Nightmares instead of him until the dragon had exhausted his firepower, and then Pitch would strike by either subjugating Toothless or simply killing him if he would not yield. Pitch wants Toothless for two reasons: 1) a magnificently powerful addition to the arsenal and 2) depriving the Big Four of their primary weapon.
Mother Gothel sees Toothless as a prize to be won. After all, a Night Fury would make a fine addition to the team. She however doesn't like to get her hands dirty as much so she lets Pitch take care of all the catching business.
Originally, Toothless was in the service of the Red Death (retrieving food for it). When Toothless met Hiccup however, the two quickly bonded and Toothless showed Hiccup the Red Death. Hiccup and his friends then helped to defeat the Red Death, though at first it seemed like they were about to lose the battle.
Without Hiccup, Toothless and Mor'du are actually quite evenly matched, strength-wise. Toothless's plasma blasts are all that the dragon can really rely upon against Mor'du as the Demon Bears' great strength allows him resistance to the Dragon's other attacks.
Having spent most of her life in her room, Elsa would have had plenty of time to read stories about dragons, both good and bad. However, upon seeing Toothless, a real dragon, she would initially be frightened of him, resulting in some sort of accident with her powers. Toothless however, upon seeing Elsa's kind and gentle personality, wouldn't be scared of her. Once she saw Toothless' gentle nature, Elsa's fear of him would subside, and she would become fascinated by him. If Elsa bonds with Hiccup, Toothless would eventually become comfortable enough to let her ride him.
Anna is someone who is not afraid to show her emotions. If she and Toothless were ever to meet, most likely on one of his adventures with Hiccup, Anna would be terrified of the the dragon, and would run behind a tree to hide from him. Once Toothless showed his more docile side however, she would be willing to approach him, and upon seeing how adorable he is, would start squealing in excitement about him. Toothless would in turn be somewhat annoyed with Anna, but if she manages to bond with Hiccup, he would be able to tolerate her and would gradually warm up to her. In time, he would be comfortable enough with Anna to let her ride him, if Hiccup allowed it.
Dragons are found to be somewhat common amongst the monster community (one working the Hotel using its fire to heat the spa), so Mavis would be less likely to fear Toothless from the get-go.In other circumstances, Mavis would be a little scared of Toothless at first, but then, once she sees how he and Hiccup are together, her thoughts would definently change. Mavis would enjoy flying on Toothless.
In How to Train Your Dragon 2, Stoick is killed by a mind controlled Toothless' plasma blast to the chest. Upon temporarily being freed from Drago's Bewilderbeast's control, Toothless comes to his senses, and approaches Stoick's body, gently nudging Stoick's hand sadly and in remorse for what he had done while under the Bewilderbeast's control, but redeemed himself for this incident by challenging and defeating the dark Bewilderbeast.
Toothless and Thornado were enemies the first time they met. After Stoick was able to tame Thornado, they became friends. Thornado and Toothless worked together to fight Alvin and the Outcasts by combining their attacks to make them flee.
Toothless appears to like Valka, probably because she is close to his rider, Hiccup. Like Hiccup and Stoick, Toothless also wanted her to come back to Berk. Toothless plays with her and understands that she is Hiccup's mother. Valka and Toothless also share a mutual love for Hiccup.
In contrast to Toothless' more playful personality, Cloudjumper is more serious but can be playful sometimes. The two appear to become friends after learning about the relationship between their riders. Now being Alpha Dragon, Cloudjumper was the first to bow down showing his respects to 'Alpha' Toothless.
Gobber was the one who made Toothless' new tail-fin. The old Viking also understands Toothless, and dragons in general, which was seen in The Terrible Twos when he gave Hiccup advice about Toothless' odd behavior.
In the books, Toothless has a huge crush on Stormfly, and often brags to her. Stormfly does not seem to care, but stays mostly by his side during How to Ride a Dragon's Storm. In How to Seize a Dragon's Jewel, Toothless blushes upon seeing Stormfly, telling her that he is "Toothless the Outcast", and points out the Wodensfang, telling her that his "sidekick, Wodensfang the Desperado."
In the movie and franchise, Toothless and Stormfly share a mysterious but pretty close friendship. They seem to enjoy each other's company, and occasionally they can be seen interacting with each other on friendly terms. Toothless seems to wish Stormfly farewell when she leaves in Gift of the Night Fury or she was telling Toothless to come with her. They are not always friendly, however. Often times Astrid's competitive nature can be seen in Stormfly, and that means that she and Toothless do occasionally get competitive. It is usually all in good fun, but sometimes the competitions can get a little out of hand, as when they were dragon boarding in Animal House. Toothless' friendship with Stormfly is probably aided significantly by the fact that Stormfly's rider is one of Hiccup's closest human friends. Not much is really known about their friendship, but it seems to be friendly and smooth, but a little competitive at times.
In How to Train Your Dragon 2, they are seen playing and talking to each other in a friendly manner, while Astrid and Hiccup are having a conversation. Their close bond is also hinted at when Toothless breaks free of the Alpha's control and calls the other dragons to aid him, with Stormfly being the first dragon shown to return to herself and join Toothless as he makes his stand. After the Bewilderbeast's defeat, Stormfly acknowledged Toothless as the new Alpha Dragon by bowing down to him.
Snotlout and Toothless dislike each other, though not as much as Snotlout does with Hiccup. However, such as in Defiant One they have been seen working together for a common goal, which was saving Hiccup from the Outcasts.
While Toothless doesn't interact with Meatlug a lot, she is a close friend. He stood next to her in Thawfest, along with Stormfly. In Worst in Show, Toothless tries to comfort Meatlug when she was sad about Fishlegs spending time with Iggy. He even looked back at her when he left with Hiccup, showing concern. Near the end of How to Train Your Dragon 2, Meatlug acknowledged Toothless as the new Alpha dragon by bowing down to him.
Toothless' relationship with Eret, son of Eret is very similar initially to Hiccup's. While Eret did originally try to capture Toothless and give him to Drago for his dragon army, they eventually become allies, and while Eret never rides Toothless, like many other former and current villains have done, they are shown to trust each other at the end of the film, even if their relationship only goes to 'acquaintance' level.Toothless, however is shown to be quite relaxed in the company of Eret when Hiccup surrendered to him, and whether this is due to the fact that Toothless trusts that Hiccup has it under control, or whether he sees Eret as less of a threat, or perhaps sees his potential for improvement, he does definitely show his carefree side around Eret more along with many other characters.
Toothless shows more of his ferocious side whenever he sees Dagur, since he is obsessed with killing dragons.
Like other dragons, Toothless fell victim of the Alpha's hypnotic abilities and was forced to attack Hiccup, but ultimately killed Stoick instead. When broken free and the large Dragon attacked Hiccup directly, Toothless used his body to shield him from the icy blast. Toothless then challenged the Alpha and defeated him by having the other dragons join him and destroyed his left tusk, becoming the new Alpha and redeeming himself for his unintentional hand in Stoick's demise under the Alpha's control and thus gaining his innocence back.
In the books, Toothless never liked Alvin. He believed the man was an Outcast, which was later proven true. In the series, Toothless doesn't hold back when facing the Outcast leader. He was shown to remember how Alvin kidnapped Hiccup back in Alvin & the Outcasts when he saw him again in Heather Report Part II. In We Are Family Part II, Toothless and Hiccup charged at Alvin, and might have killed him if they hadn't been tied up. In Cast Out Part II, Toothless was not thrilled about having Alvin join him and Hiccup to save Stoick. He even smacked him with his wings when Alvin was joking about his death grips. Toothless did seem pleased as he and Hiccup watched Stoick and Alvin make up though, probably gaining slight trust in him.
In Tunnel Vision, Toothless met a new enemy: the Screaming Death. This large Dragon goes after him and Hiccup more than the other Dragons, most likely due to Toothless attacking the Screaming Death more often. Hiccup and Toothless were able to lure the albino Dragon into colliding with a sea stack, and injuring its wing. The Screaming Death obviously remembered this when they met again in Appetite for Destruction, as Hiccup and Toothless were its main targets other than sinking the islands. In Cast Out Part II, Toothless is happy to see the Screaming Death reunite with it mother.