Boris Tollar, is Caillou's father and also his secondary caregiver. His parents are Caillou's grandparents, Grandma and Grandpa. He would often ground his son Caillou whenever he did something bad. He has been appearing in almost every episode since “School Daze: The Movie”.
Boris is an angry and abusive person. He would always ground Caillou for doing bad things. Sometimes, he would take it too far with the punishments. Like for example, he cut off Caillou’s penis for peeing on the teacher. However, after the events of the Christmas Chronicles series, he started treating his son with love and care again, just like he did in the original show. In "Endless Summer", his wife Doris found out that he was cheated on her with Elena, and the two got divorced shortly after. Boris got custody of Caillou and Rosie, and they are now living In Quahog, Rhode Island, though Caillou would usually go back to Franklin to help Tom and co. with school. During his off-time, he would hang out at the Drunken Clam with Peter.
Boris has tan skin, brown eyes, and brown hair. He mainly wears clothing with the colors green, red, and blue.
In Caillou, he had short hair and wore a green long-sleeved sweater with a red border, long blue pants, and red shoes with yellow buckles.
In School Daze and several Caillou gets Grounded videos, He has longer hair and wears a green hoodie with red laces, his green sweater underneath, blue jeans, and red sneakers, which are very similar to his son's.
In Virtual Paradise, Boris wears a green short-sleeved polo shirt with a red collar and trim, blue shorts with red highlights, and red sandals.