The Bears are Cyril Sneer's additional henchmen, workers, soldiers, spies, etc... Anything that suits his needs for that particular episode. They are not very smart, and also shown to have a huge temper, which is shown in the episodes Mom's the Word! and End of the Line! They are also very clumsy as witnessed in Power Trip when Cyril makes them rush to complete his power dam (which later collaspes) and they end up dropping building materials, getting thrown into a cement mixer, and and other kinds of mistakes.
Bert with two of Cyril's Bears