Prior to series start
Holger moved to Toronto from his homeland of Sweden and started to go to A Nigma High in the 9th grade. Holger had been cornered by a crowd of Tormentors led by Irwin Dexter but had been defended by Lee Ping and Camillio Martinez and the three of them have been inseparable ever since.
He claims he had a girl back home but appears to have broken up with her before returning to Canada ("Summer Fun").
Holger was present at the prank and even danced for a short amount of time during it. Though initially disliked by the school football team he became friends with them after he became their water boy. Not only does he provide water but he also provides food, cleans up after them and constantly goes out of his way for them. 
After learning that Lee used to be friends with Irwin Dexter, he was shocked that Lee use to be friends with someone he isn't now. This led to the belief that Lee might break off their friendship and thus he goes out of his way to help him, even if it has been known to get him into situations that he can't get himself out of. ("Math Math Revolution")
Despite his occasional naivete Holger has proven himself an expert in the fields of cooking (able to make gourmet food from stuff he finds in the cafeteria), spa care (frequently treating himself at his host home), acrobatics (still working on the landings), contortionism (comfortably able to fit inside a locker and even dress inside it at one point), dance (named the school's official choreographer), and stealth (able to run circles around the highly trained Principal General Barrage) which on numerous occasions he's been able to use to gather valuable intel on Lee's suspects.
Holger has entered a blossoming romantic relationship with the Mathlete Greta Von Hoffman. Holger's friendship with Lee and Camillio becomes strained when he discovers evidence of Camillio's involvement with The Prank suffering increasingly irrational theories about Camillio's involvement and unsure who he should side with.
The tension between Lee, Holger and Camillio reaches a height during the yearly student body elections. With both Lee and Camillio running Holger ultimately realized that as long as they were fighting he couldn't remain friends with both of them and thus decided to remain friends with only the winner of the election. Luckily however Lee soon realized that Camillio was brainwashed during the prank.
With both Lee and Camillio on speaking terms Holger begins taking a more active role in their affairs, making himself the unnoficial bodyguard of "President" Camillio, as well as having the free time to focus on his relationship with Greta going on their first official date. He also plays a critical role in decyphering Radcircles identity winning a necessary bet against Irwin in exchange for making him decrypt the phone.
However Holger's relationship with Greta hits a rather sore note when as part of Vice Principal Victoria's Brainwashing experiments he is forced to ask Kimmie McAdams out to the dance. Luckily for him his true feelings for Greta resurface and with the aid of Cyrus Xavier and the Dudes of Darkness wins her back from Ed McFeeney just in time to rally Lee's allies against Vice Principal Victoria after Lee was expelled and take Greta to the Dance.
Holger continues to aid Lee in his quest to clear his name, including planning a rescue mission to get him out of Alaska and once Lee is un-expelled, attempted to help Lee break out of the new and improved detention room, tried to help save the Tazelwurm, joined Lee at his meeting with Lynch, solved the mystery of who stole Lee's bag, tried to help steal the Key back before finally being struck by the pyramid's blast.
Additionally Holger's relationship with Greta crumbles: as part of his attempts to make Lee's life difficult Bradley Von Chillstein steals Greta as his 'girlfriend.' Though Lee was able to break them up Steve also develops a crush on Greta and begins playing stupid to spend more time with her, which Holger ultimately exposes and after a series of 'love tests' devised by Kimmie McAdams she breaks up with both of them.
As a result of his exposure to the Pyramid Holger mysteriously gains the power of Precognition, and uses it to great effect to help Lee and Biffy sneak into the Council's underground base, as well as helping to rescue Lee when he is cornered by the Council's enforcer The Serpent inside said base. Holger has a disturbing dream where he witnesses Lee being crushed by a "Big Chicken" which turns out to be true in a metaphorical sense.
When the school suffers a lice outbreak Holger and Biffy team up to figure out exactly what kind of powers Holger has and concludes that he has the ability to "smell love." Additionally he also helps Lee and Biffy take advantage of the quarantine to hunt the Serpent down when he's loose in the school, failing miserably though. Holger also agrees to help Camillio look after his sister Angelina Martinez.
Later, while experimenting with his love powers, Holger learns of the budding romance between Chopper McNeal and Beth that is doomed to fail thanks to the actions of Biffy. As a result Holger sets out, and succeeds, to bring them together. Later on Holger visits the Ping family home where he accidently gave Lee's dad (Alfred Ping) fish-stuffed pizza, oblivious to the fact that Lee's dad is allergic to fish so he tries to make it up to Lee's family by repainting their house wall. Unfortunately, the Serpent broke in and interrogated Holger about the whereabouts of Lee's parents and even threatened to cut all of his hair, but luckily Lee had arrived just in time to to chase the Serpent off. Later, Holger visited Lee's dad in hospital to get his forgiveness for accidentally almost killing him. Seeing that the Serpent had arrived at the hospital, Holger took mr Ping to safety. Together he and Lee faced the Serpent, who revealed his blood relation to the Pings before taking Alfred Ping away. Holger and Lee were shocked upon the revealation of the Serpent being Lee's long-lost brother. After the two make their escape, Holger calms broken and confused Lee by giving him a reassuring hug and gets a key from him to his protection.
In "Band of Heroes" as the gang had to leave Cam behind, Lee, Holger and Biffy set off to Coral Grove where they rescued Tina and Jenny. As they were about to escape, the security cameras get alerted and immediately closed the prison doors, leaving them all trapped inside. Holger and Biffy were able to steal Cassandra's iron mechanical flying suit, and together he and Biffy saved Lee from being caught by Cassandra's allies by crystalizing all of them with the apparent end to the conspiracy.
Holger is a typical fish out of water who tries his best to adapt to life in a new country. His English is not the best, and he often doesn't understand social cues, taking a lot of things literally. As a result, many people at A. Nigma High don't understand him, or even pick on him for being "weird". His best trait by far is his kindness, as he's always around to offer moral support to Lee and Cam when they need it. He's very loyal to his friends, and his dream is to be best friends with Lee and Cam "til old man times".
He is very athletic, often preforming complicated gymnastic tricks with relative ease. Dancing is one of Holger's favourite pastimes, and he's shown to be quite good at it in numerous episodes. Holger is also shown to be quite artistic, as he's skilled with both painting and drawing. He often expresses his feelings with art, such as drawing a sad clown in his notes when he was upset.
Holger can be quite sensitive and quick to tears at times. He tends to feel others' pain, and will get very stressed out if his friends are unhappy or fighting. When this happens, Lee usually calms him down and sets the record straight.
Lee Ping & Camillio - since the two protected him from the bulliying back in 9th grade, Holgar considers Lee and Cam his bestest friends. Sometimes it seems like he has some kind of a slight obsession with them, as he knows lot's of personal things of theirs and even carries their pictures. Holger in fact has stated that he wishes to be friends with Lee and Cam to the "old man times". Holger loves making his friends happy and helping them out any way he can, even when he fails and makes things worse. He is the one to cheer up and lighten up the mood when everyone's down. Holger is friends with them both equally and has a hard time when Cam and Lee have fights, since he cannot choose which side of the conflict he should support. However once all the problems are solved, all three become stronger like never before.
Principal General Barrage - originally Barrage was annoyed at Holger and Cam because they were laughing at him during his introductury ceremony. In addition, during the football try-outs he was quickly cut for bad football skills. However when he then started to try-out for water boy Barrage complimented him on his excellent waterboy skills and gave him the position. Later during the school play, Barrage was horrified by Holger's dance moves.
Jocks- Holgar became waterboy this year of tenth grade and has seemingly befriended the Jocks to the extent that they seem to enjoy his cooking and water. He is certainly treated better then their old waterboy Ed McFeeney whom was wedgied, beaten, and generally treated horribly by the Jocks on a daily basis.
Ed - originally it is implied that Ed and Holger were friends as seen when sharing breakfast and Ed comforting Holgar after he was cut. However after Holger took the position of new water boy Ed came to hate him and is jealous that he gets more respect as water-boy than he ever did. In addition to this Ed has developed a crush for Holger's "true love" Greta as a result the two's rivally has reached new heights.
Greta - Holger and Greta started to develop a mutual romantic feeling to each other shortly after Lee's confrontation with Greta's fellow Mathletes. Later, when hypnotised by Victoria before the school dance, Holger starts to go out with Kimmie, straining his relationship with Greta, while Greta goes out with Ed out of jealousy. However, they get back together whilst trying to stop Victoria's nefarious plans for the dance. The next trial occurs when the leader of the Jocks clique Steve, develops a crush on Greta and goes on a study date with her at the mall. Holger numerously rivals Steve, but ultimately, too preoccupied with the school conspiracy, Holger backs off, letting Steve and Greta eventually hook up. As of "Date With Destiny", Holger and Greta have peacefully broken up.
Holger is mostly seen in a comic relief role and occasionally is the focus of B-stories on the show. While he doesn't seem like it, he is very adept in espionage; capable of trailing even Barrage with ease and scanning an entire team of jocks without getting caught. Holger is also a skilled dancer, his love of dance is to extreme proportions and he can do extremely complicated moves that leaves even Barrage in shock.
When the Prank Song played on the first day, Holger (along with a handful of other students) were seemingly unaffected by its hypnotic effects, with Holgar even dancing most of the time, though after the song was improved, Holger was brainwashed; he was eventually able to over come it on his own showing to be at the very lease resistant to it's hypnotic effects, mostly because of his love for Greta.
According to Barrage, Holger is a master interrogator: he's so annoying the "perp" would tell him anything he wants to know. He has impressive deductive abilities, though he refuses to explain how he figures out the "case". Holger also seems to be knowledgeable about certain things like being able to correctly tell the make and model of a camera at a glance and being able to avoid capture by multiple adversaries.
After exposure to The Pyramid Holger gains the power of precognition, able to navigate the school blindfolded, operate The Council's equipment just by randomly guessing and expertly avoid enemy adversaries. Holger is unaware of the nature of his new power and has tried, and failed repeatedly, a variety of other abilities as well ultimately concluding that he has the ability to "smell love" which implies a degree of empathy as well.
Holger has also learned that by drawing with his eyes closed he can accurately predict scenes of major emotional stress within the near future.
- "Holger has... an idea cake!" - "Mummy Ping And The Snake Man Of Evil"
- "I'm too wonderful to die!"
- "Hello? Love?? What is problem?!" - "The Common Denominator"
- "Did someone mention something about PIE?"
- "Is point of ride to 'not' die? So..."
- "Most yesfinitely!"
- "Don't like me?!? Impossible! Everyone loves Holger! I love Holger! I love him so much!" - "The Down With Lee Club"
- "Li! It is me, Holger! H - O - L - Ger" - "Friday Night Bites"
“Lanky, eccentric, and good-hearted, Holger is the guy that makes Lee and Cam a tight little trio-or "friendship goofen-burger" as Holger might say. An exchange student from some European country that Lee and Cam have never heard of, Holger struggles with English, but usually gets his main points across: he likes unicorns with sideburns, tapioca pudding with grated ox tail on top, and "disco party times." Holger helps Lee on "missions" and uses alter egos when going undercover.”
- Holger is a fan of Ace Von Chillstein.
- Holger is a skilled dancer and enjoys it every possible moment.
- Holger is not good at charades nor is he "getting any better".
- Holger has a habit of adding particle "-times" in his speech which denotes some kind of situation, emotional/moral state or limits of time.
- Holger collects pens of all sorts, which has a bad habit of being destroyed in comical ways.
- Holger believes that he is a really good juggler, while in reality he just throws items up in the air.
- Holger has had at least three phones: he dropped his first one which Barrage found and crushed when a text was sent to it that infuriated him. Holger's current phone looks exactly like his old one and it is also waterproof, which was destroyed by Barrage in the incinerator, the third, his phone from Victoria, was accidentally destroyed by Camillio.
- Holger carries gloves with him, which he uses to slap people who insult his dancing and to challenge them with as well.
- His spy uniforms have an 'H' symbol on it, alluding to his name.
- He claims to be especially scared of Barrage's "robot leg".
- Holger claims to have a "bad list" of people whom he doesn't like or he's mad at.
- Holger is often picked up by various characters for his bizzare English and poor vocabulary. When asked by Chaz if his language ever improves, Holger replies, "Why for improve? Holgar's English is already in the perfect-times!"
- According to the show's creators, in Canada Holger supposedly lives with his father, who is an international spy. This may explain just why Holger is so skilled at spying and camouflage.
- Detentionaire TV series: Season 1, episode 1 - "Blitzkrieg Bop'd"
- Detentionaire TV series: Season 1, episode 2 - "Jock and Roll High School"
- Detentionaire TV series: Season 2, episode 2 - "The Cam-didate"
- Detentionaire TV series: Season 1, episode 8- "Disco History Times"
- Detentionaire TV series: Season 1, episode 13 - "The Hair Incident"
- Detentionaire TV series: Season 1, episode 7 - "28 Sneezes Later"
- Detentionaire TV series: Season 2, episode 1 - "If the Shoe Fits"