Boris is Caillou and Rosie's father, the main protagonist of the Caillou gets grounded videos, the main deuteragonist of the Caillou Gets Ungrounded videos, and the main antagonist of the Life Without/With Doris franchise.
He's well known for having a severe grounding fetish and being an infamous criminal in GoCity. He is also in most videos quite abusive towards Caillou, and in some videos he even goes to extremes (such as raping or killing Caillou, and torturing him). Boris is the main reason why many people hate Caillou Gets Grounded videos and call them out to be child abuse when it's only fictional. In some videos he is non-abusive, because like Diesel Bustershe has a split personality and one is nice and fun while the other is wicked and hates kids, and he mostly uses the wicked one.
Boris also has a third personality named Boris The Teeth Guy (aka Red Boris) who has red skin, a huge mouth and big eyes, constantly swears and is a violent, angry and extremely evil maniac who takes pride in his own teeth (he probably used to be part of Boris's multiple personalities, but then got out of Boris by himself because of GoAnimate Logic). Sometimes Boris turns into Red Boris when he's extremely mad until he cools down, but this rarely happens.
Go Animate Boris generally has a very complex, disturbed and egocentric personality. He always acts out on his violent and hateful desires towards Caillou. He seems to use Caillou and Rosie for his own personal gain and acts like a huge bitch, and he thinks they're disappointments. This is because either he was probably abused as a kid or he just downright hates kids as a whole. He is one of the loudest screamers in the Anderson family.