Bloo – Mac's 5-year-old imaginary friend and best friend who resembles a simple, domed cylinder. Bloo is sometimes self-centered, egotistic and narcissistic almost to the point of psychotic delusion and has a knack for getting into trouble. However, he still has a good heart and apologizes for his actions. Bloo loves paddleballs even though he can't make the ball hit the paddle (though the only time he was able to do it was in the episode "Let Your Hare Down"). His full name is "Blooregard Q. Kazoo". He became increasingly mischievous over the run over the series and is shown to have bad memory some of the time.
Bloo was one of the surviving Foster resident when their world was conquered which led to formed the first Society member, even he was the first member, he took on a training lesson at the Sentinel Academy, that is he would make it graduate sooner if he just let his ego down abit.
Bloo also appeared in Ultima story where he join with Nick on the first encounter and on a quest recovering all of the Chaos Emerald.