Sven is a major character of Disney's Frozen franchise. He is Kristoff's reindeer and best friend. Being a deer, Sven does not talk and only makes grunt-like vocals. However, Kristoff occasionally voices Sven's thoughts using a goofy "reindeer voice".
Vote which fictional character would naturally fit in-universe with a big-named franchise! No time-travel, no interdimensional crap, no "Pooh's Adventures", they would just exist in-universe.
