Cubix is a friendly and helpful robot originally created by Professor Nemo and later owned by Connor. He can transform into a variety of different types of vehicles, including a hover bike, an airplane, and a helicopter. He can even fly without the need to transform into a vehicle.
His body is composed of a number of modular cubes and constructed out of a highly resistant metal that is capable of withstanding devastating amounts of damage. Each cube contains a different gadget with a solution to almost every dire situation. When it comes to fighting, Cubix is exceptionally strong. He is powered by a Solex generator which is rumored to be the ultimate power source, but nobody knows exactly how it works.
Cubix has an orange symbol on the back of his head, which is later revealed to be the mark of Professor Nemo, who put the mark on all of his robots.
At the start of the series, he is broken and no one can figure out how to make him work, giving him the nickname "The Unfixable Robot". However, the idea of friendship seems to be a key concept in order to activate him; when Connor says the word "friend" while saying goodbye after unsuccessfully trying to fix him, Cubix starts to repeat this word inside his head, clearly generating some kind of response to it. Connor then brings Cubix back to life by trying to save him from a collapsing building. This action jump-starts Cubix's EPU, who then saves both himself and Connor from the falling roof. Successfully repairing Cubix also gains Connor access into the 'Botties' group.
At the end of the first season, Cubix sacrifices himself during the battle against Kulminator, flying directly into its EPU. The ensuing destruction causes Cubix's own Solex reserve to be depleted, exploding along with Kulminator's Solex energy. Due to having no Solex remaining, Cubix shuts down and is unable to be repaired by Connor, Hela, or even Professor Nemo. However, he is later rebooted after the remains of the crystallized Solex coalesce and fly directly towards him. Cubix claims it was Connor's determination and continued belief in him that caused the Solex to revive him.
Cubix initially lacks speech capability (possibly because he might be a prototype or old model, or because he did not have enough Solex to operate at full capacity), while speaking seems to be common place among other robots. Usually he just repeats what people around him say. His eyes also change to reflect his mood or emotions. However, after he absorbs more Solex and reboots, his speech functions improve greatly and he becomes capable of forming sentences and dialogue, much to everyone's surprise.
Cubix has a power up module with additional parts that, when added to his structure, drastically increase his strength and speed. However, the added parts require a massive amount of power when installed and must be removed within three minutes of activation or Cubix's power source will overload and he will blow up.
Cubix's transformation process can be interfered with, allowing another modular robot to add his own parts into Cubix when he transforms. Kilobot has done this when Cubix was changing into his normal configuration by adding his parts into Cubix's form, merging into his and forming "Kilo-Cubix".