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Kristoff's lovable pet reindeer.
- Action Pet: His biology has made him this; capable of leaping a wide ravine, surviving frigid waters, tearing through blizzards at breakneck speed, keeping ahead of wolves while towing a large sled, and pulling Kristoff and Anna out of holes and away from trouble while only eating a bunch of carrots, his favourite snack, and probably moss.
- Adaptation Name Change: In the original story, his name was Bae. Here, it's Sven.
- Adorkable: Mix in his clumsiness, love for carrots, and facial expressions, and Sven counts.
- All Animals Are Dogs: Has the mannerisms of a dog more than a reindeer, and his official character description even describes him as "a reindeer with the heart of a Labrador." This is Played for Laughs and inspired by how the reindeer the research team met reminded them of dogs with their panting and scratching mannerisms. Lampshaded in A Frozen Heart when Anna thinks "[Sven] reminds me of a puppy".
- Amplified Animal Aptitude:
- He's clearly got a better grasp of what's going on than a normal reindeer might.
- In Frozen Fever, he can slice a three-tiered ice cream cake into perfectly straight, equal-sized wedges... with his antlers.
- Badass Adorable: Sven is also an adorable reindeer.
- The Cameo: In Moana, Maui accidentally transforms into him while fighting Tamatoa.
- Character Tics: He has a tendency to lick both people and inanimate objects. Kristoff, Olaf, the staircase at Elsa's ice castle, carrots, you name it, he's probably licked it.
- Childhood Friends: Has known Kristoff since they were kids.
- The Conscience: To Kristoff. Played with, as most of the time, Kristoff himself is the one actually making the argument. It's played straight near the end, though, when Sven proves he doesn't need Kristoff to speak for him to get his meaning across.
- Cool Pet: This reindeer jumped a gorge! That's pretty awesome.
- Cute Mute: This reindeer is silly, snarky and lovable, and yet he does not say a single word the entire movie.
- Disney Death: It's small in comparison to everything happening when it does, but he manages to buck Kristoff off to safety during their breakneck run in the climactic blizzard when the fjord's icy surface cracks underneath them and sends him into the freezing waters below. It takes a harrowing moment, but he surfaces not long after. This is justified, since reindeer/caribou are easily capable of swimming even in icy arctic waters; the main peril comes because the audience knows if a horse or human fell inside, it would probably be fatal.
- Happily Adopted: As a young reindeer, he and a young Kristoff were taken in, loved, and nurtured by trolls.
- Heroic Sacrifice: Almost, see Disney Death above. When he surfaces, he urges Kristoff to keep moving while he's stuck out on a small ice platform.
- Heterosexual Life-Partners: He and Kristoff were both adopted by the trolls and, until Anna, was his only friend.
- Homeless Hero: Implied to be this with Kristoff, after the latter was thrown out of Oaken's shop they go to a barn. His family lives out in the open because they are trolls.
- Interspecies Adoption: Sven (reindeer) and Kristoff (human) have a familial bond with their family of trolls.
- The Lancer: For Kristoff. Not only as his steadfast backup, but Sven creates a contrast with Kristoff by being the more reasonable and generous of the two.
- Loyal Animal Companion: To Kristoff. The two have been together since childhood.
- Nice Guy: Sven is sweet, loyal, playful, and has a strong moral center.
- Morality Pet: A literal, and downplayed, variation. Sven acts as an unusual version of this, one who cannot talk, but gives Kristoff looks that Kristoff interprets as encouragement to help Anna.
Kristoff: When a reindeer herder finds a reindeer left behind to die /the herder saves the reindeer's life /and the deer makes him a better guy.
- Lampshaded Trope in "When Everything Falls Apart," a song from the Denver stage show and included in the Broadway Original Soundtrack:
- Non-Human Sidekick: To Kristoff, because he's a reindeer.
- Only Friend: Sven has been this to Kristoff since they were kids.
- Parental Abandonment: No idea what became of Sven's mother or herd, any more than we know what happened to Kristoff's parents.
- Plucky Comic Relief: Like Olaf, he provides levity in a number of places; however he's not a magical creature and still quite vulnerable. He proves his pluckiness by taking a dive into a frozen fjord and coming out relatively none the worse for wear.
- Shipper on Deck: For Kristoff and Anna, such as convincing him to go back to her.
- Sidekick: To Kristoff and Olaf in market sales.
- Silent Snarker: When he tries to convince Kristoff to admit his feelings to Anna.
- Talking Animal: Downplayed; he cannot talk, but Kristoff likes to pretend he can, playing both sides of their conversation. Also, Sven makes appropriate gesticulations for his part of the conversation. He just can't make the sounds himself.
- Nearly Normal Animal: Of the "Almost Normal" variety. He doesn't talk, but is still clearly a Shipper on Deck, nudging Kristoff toward Anna twice and giving him a rather human-like expression the first time, and occasionally shows some doglike tendencies.
- Adapted Out: He doesn't appear in the movie's stage adaptation.
- All There in the Manual: He isn't named in the movie and shorts, but all printed material reveal his name to be "Sitron."
- Amplified Animal Aptitude: Like Sven, he's clearly a lot smarter than your average horse. He steadies the boat Anna falls into, follows Hans's lead in bowing, and when doing so tips the boat again, tries to correct it.
- Cool Horse: A Fjord horse, going by his coat and mane.
- Multicolored Hair: Sitron has a white and black mane and tail, and is buckskin (tan with darker legs).
- Nice Guy: Very sweet and a stark contrast to his owner.
- Non-Human Sidekick: Hans's horse.
- Skunk Stripe: He has a black streak of hair on his mostly white mane, and a larger black streak in his tail.
- Unwitting Instigator of Doom: He knocks into Anna, prompting her and Hans' meeting and setting off Hans's plot to marry into Arendelle's royalty.
- What Happened to the Mouse?: Disappears from the film altogether before Hans's true plans are revealed. Even the Tie-In Novel A Frozen Heart, which gives a Broad Strokes retelling of the film's story with a greater emphasis on Hans and features new scenes with Sitron, completely forgets Sitron exists when Hans is sent back to the Southern Isles alone, so Sitron could either still be in Arendelle or could have been found and sent back to the Southern Isles.