Throughout the vast, 3.5 year lifespan of the TBTTRAH Series, there have been multiple main characters. Here's a list of some of them.
The Tahus, or Tahu & Tahu as they prefer to be called, are the co-leaders of the House and the Bionicles living inside of it. The group consists of a Tahu Mata set and a Tahu Nuva set, both of which have been with the group of Bionicles since they first managed to come to life. Tahu is a hot headed, but fiercely loyal, leader who is very devoted to leading the Bionicles correctly. He has a strong disliking for Pridak, the rest of the Barraki, and really any other trouble makers at the house. Tahu is also a Boston sports fan for some reason, and has been known to hit people with baseball bats just for being Yankee fans.
Tahu Nuva, on the other hand, is a patient and levelheaded co-leader that usually gets Tahu out of the trouble that Tahu gets the duo into. Tahu Nuva has an obsession for windows, however, and goes beserk when a window is smashed. Tahu Nuva, due to his calmer nature, has never been anywhere near as many crazy situations as Tahu, and thus has not suffered from any signs of insanity.
Pridak is the arrogant, slightly deranged leader of the Barraki and is the biggest troublemaker at the house. He is constantly trying some new creation or making some new plan, which usually ends up with someone getting hurt. The "someone" is not limited to other people, however, as he once attempted to kill Mesonak with a knife and ended up getting his right arm sliced off. A quick surgery by Toa Zehvor Brenmac managed to save his arm, however.
Pridak has a strong hatred for Mesonak because of this incident, and is currently planning some sort of revenge. He also happens to dislike Tahu because of his strict-ness(though it was Tahu's quick thinking that saved his arm), and dislikes 4 Mask as well for kidnapping him. Pridak's best "friend" is Zaktan, and he is usually able to talk Zaktan into getting the Piraka to join the Barraki for Pridak's plans that involve more than 6 people.
Main article: Toa Zehvor
The Zehvor are a "Toa" team that has gain reknown throughout the galaxy for multiple accomplishments, most of them including stopping Xenon spread. When not busy doing this, the team can generally be found at the house playing video games or snacking on frozen foods. The team is, in order:
MT: Leader of the Zehvor, one of the "calmer" influences on the team.
Sonu: 2nd in command, another relatively sane person. Has a unsurpassed love for Halo.
Brenmac: A veteran member of the team, has his own list of Brenmac facts comparable to those of Chuck Norris.
Mr. Matoro: The only Matoran on the team, is almost always found packing some sort of heavy weaponry.
Levacius: An RPG obsessed Lightning Toa who can always be bribed with an offer of chicken wings.
Kopeke: Formerly known as Tarakavaseargent and arbiter. One of the tougher members of the team, has attempted to cook Levacius in the past.
Mesonak: Downright insane, but smart. Once cut off Pridak's left arm and got sued for it.
TLhikan: Shares Levacius' love for chicken wings. Doubles as a hitman for Tahu Mata in his spare time.
Gorgnak: Formerly known as Rahkshiking, has an odd obsession with rocks.
Dakama: A fire and metal Toa who almost always gets stuck working with a crazier team member and hates every second of it.
Kpik: A long lost friend of MT who was reunited a while ago. Loves ice cream and annoying Piraka/Barraki.
Burnmad: Always in a perpetual state of rage. One of the more recent additions.
Blackout: A Makuta/Toa cross who was first introduced to the team after kidnapping MT. Has a weird affinity for dragons.
Shadow: The only female member of the team, a powerful scythe wielding Makuta who Blackout has some animosity towards.
Samzoraz: A Lightning Toa who recently disappeared.
Assassin: A powerful Toa who was assigned to guard planet Vundas. Not seen since the planet fell.
Hovoki: Toa of Sprite who was nearly killed in combat and is still recovering from injuries.
iBrow: A rather quirky addition to the team. Always has some sort of insight to provide to a situation.
Shadrahk: A Rahkshi who occasionally shows up to annoy someone or push a person out of a plane.
JL: A new member of the team, a young Toa of Storm with no memory of a important history connected to Xenon, and the supreme skill of a Freelance warrior.
Zaktan is the leader of the Piraka and one of Pridak's few friends. He is somewhat adventurous, and is usually quite intelligent, with the exception of when an emergency occurs. In an emergency, Zaktan completely "freaks out," and goes crazy, spitting out words related to whatever happened until the person he is talking to can figure out what he's saying.
Prior to the house's destruction, Zaktan was much "crazier," and was well known for acting randomly in order to frustrate Tahu or other house members. Ever since that fateful day, however, Zaktan has learned that life is much more precious, and he doesn't act as randomly now.
Main Article: Omega Turtle
Omega Turtle is, true to his name, an Omega Turtle. He was never given another name because he "wanted to be like Makuta and just be named after his species." Since then, Makuta was given the name Teridax, and Omega lost all respect for his former hero.
Omega is amazingly intelligent for a member of his species. His personality is most similar to that of Tahu's Nuva, though he has no problem beating someone up if they become a nuisance. He is best known for his unexplainable ability to eat things up to 6 times his size. He has incredible strength and speed to go with this method of attack, as well as the power to spin jump infinitely in the air. Omega's best friend is MT and the two have teamed up to take down some of the most notorious house villains in the past.
4 Mask is a Rahkshi of Xenon. His home location is unknown, but what is known is that he takes a certain delight in watching the house residents suffer. He was once a well-standing inhabitant of the house, but after a failed attempt to take it over, he was kicked out. After several attempts to destroy the house, he was confronted on board a space station by MT and 5 Mask, and "killed" when the space station was destroyed.
However, he returned nearly 2 years later, in what was dubbed as a: "ridiculous spin off of Attack of the Clones." 4 Mask, with the help of some nifty teleportation, managed to sneak into the Coffee Mines in the house. There, he found DNA strands of many of the deceased house residents, and then took those strands back to his base on the planet Vundas. However, unbeknowest to him, the clones did not maintain their intelligence, and went beserk.
In the midst of all this, 4 Mask was assigned by the Dark Lord to raid a IUPD planet. He did successfully, but was encountered by MT and Kopeke. After a quick skirmish, 4 Mask managed to chase the two Toa off and eventually bomb the rest of the city. 4 Mask returned to Vundas, and, after finding his base of operations discovered by yet more Zehvor, decided to hightail it out of there, kidnapping Mesonak and Sonu. The kidnapping backfired, however, as Mesonak managed to free Sonu, and then Sonu sliced off 4 Mask's left arm.
4 Mask was later encountered by MT in the middle of the planet Kyrell. In a furious attempt to kill the Toa, he went bezerk and supercharged himself with Xenon, deciding that he was willing to kill himself in order to finally kill a Zehvor. Ironically enough, MT then went on to kill him with his own Xenon missile.
Nocturn is a kind but dumb amphibian with some alliance to the Barraki. He is always hungry and can nearly always be found in the refrigerator, much to Tahu's chagrin. Nocturn's best and only friend is Gadunka, and the two are always together unless a natural disaster has occurred.
Gadunka is Nocturn's friend. He has no care for the Barraki whatsoever, and, like Nocturn, can nearly always be found in the fridge. He is a bit more intelligent than Nocturn, however, he lacks any ability to speak in the English language. The one language he can speak is, "Gadunka," and so far, only Hahli Mahri and Nocturn are able to understand him.
Xplode is Pridak's arch-rival and one of the more cynical characters in the series. Xplode always has some negative comment to make on the situation, which has more than once gotten him into trouble(i.e. Omega Turtle). Pridak hates him so much because Xplode once pushed the Barraki down the chimney into a fire. Xplode spends most of his time on the couch watching TV.
Xplode, although he has always regarded Pridak as an idiot, never really started hating him until Pridak ditched him at a pool store(Pridak took the car that he and Xplode had used to drive there and left Xplode and Fire Lord behind). Ever since that day, Xplode has been looking for opportunities to kill Pridak, though they have all been thwarted, usually by Pridak's ignorance, amazingly enough, or someone unwittingly getting in the way.
Brutaka is the stair-o-phobic card playing resident of the household. He is nearly always found in the middle of some card game, whether it be poker, go-fish, or his odd combination of the two, "fisgoker." As previously mentioned, he is terrified of stairs, and was the reason the Bionicles installed an elevator in the house before its destruction(much to Brutaka's annoyance, the elevator has not been restored since the house was rebuilt by the "Golden Toa.")