Sven is actually a combination of two characters in Beast King Go Lion. Takashi Shirogane was the original blue lion pilot who was killed in episode 6, and Ryou Shirogane, Takashi's brother. Since they looked alike, WEP simply decided that Sven would survive the events of episode 6 and be treated as if they were the same character. In Sven made an appearance in Season 3 of the show. Josh Keaton only discovered that the character had a Scandinavian accent the day before the recording.
Sven was part of exploratory team sent by the Galaxy Alliance to planet Arus. He was captured and sent to Planet Doom. After escaping planet Doom he got to planet Arus and became so pilot of the blue lion. Sometime later Sven saved Lance from an attack from witch Haggar. His injuries resulted in Sven being sent to a space hospital and eventually being replaced by Princess Allura, ruler of the planet Arus. Sven reunited with the Voltron Force where they helped Romelle escape planet Doom.
Voltron Force
Sven makes an appearance in 2011 Voltron Force. Sven appears in the episode in “Ghost in the Lion.” Sven was a former pilot of Blue Lion. He has been infected when Haggar's cat had attacked him and eventually the infection progressed so he had to stay in a very cold environment to keep the infection from overtaking his mind.
Voltron: Legendary Defender
Sven is an alternative reality version of Shiro and a member of the Guns of Gamara, a rebel faction fighting against the Altean Empire that ruled his reality Universe for 10,000 years. He died protecting Felix after taking a energy lance for him. Sven appears in an episode called Hole in the Sky on Sven's dies to save Lance and comment about being taken to a space hospital are references to Sven's fate in Voltron: Defender of the Universe, which this character's existence is a homage to. According to Joaquim Dos Santos, the original Sven was often a topic in the writer's room because of how often thinking about inspiration from the original Voltron show led to someone doing the character's voice.
Comics
In the 2011, Devil's Due comics the character full name is revealed as Sven Holgersson. The comic book version of Sven depicts him as 27, the oldest member on the team. Unlike his cartoon counterpart, the comic book Sven is given much further depth, and plays a major role. Much of Sven's past remains unknown, except that he was a former member of an elite Navy squad similar to the SEALS. During an insurrection in a small South American country, a serious miscommunication caused a foreign national Sven was supposed to extract to believe Sven was an assassin and opened fire. Sven was left with no choice but to fire back, protecting himself and eliminating the extraction target. He was then placed on "administrative leave" until he was approached by Colonel Hawkins to join a team of outcasts to search for the legendary robot Voltron on the distant planet Arus. Sven was possibly the most anti-social of the group, but this is possibly due to being the oldest and most mature. Unlike in the cartoon, Sven never got a chance to properly form Voltron, or even get to wear his classic black uniform. This is due to him having a brain defect that caused the magic of Voltron to somehow reject him. This brain defect caused him to fall under the influence of Queen Merla and Haggar, under which he betrayed his friends and Arus by stealing files from the Castle of Lions' control room. He was then placed on a mission alongside Prince Lotor, during which the two found themselves having to survive together and try to trust each other. During a conflict that erupted later, Sven apparently crash-landed on planet Pollux, where he was discovered by Princess Romelle. Due to the comic's hiatus, what path Sven's tale would have taken from that point remains a mystery.
