Bloo is Mac's 5 year old imaginary friend whom Mac created when he was 3 years old. Though, Bloo's completely the opposite from Mac as Bloo is a immature trouble maker who gets jealous very easily especially over Mac's other imaginary friend Cheese. Bloo is one of the main characters of the show Foster's Home For Imaginary Friends as the series mostly focuses on him adjusting to the home and going on adventures with his owner Mac. Bloo also thinks highly of himself as he claims he's "the best imaginary friend ever.".
Despite Bloo's rowdy personality he does care for his friends deeply whenever something happens to them. Showing that Bloo really does have a heart and feelings. One time his friend Eduardo was thought to be shot and Bloo burst into tears hoping that Eduardo would be okay. Bloo's favorite sport is paddle-ball even though he never makes the ball hit the paddle making him believe that all paddles are broken.