Blooregard Q Kazoo "Bloo": Bloo the self proclaimed "Best Imaginary Friend Ever" is a small blue friend and Mac's best buddy. Bloo is prone to be very selfish, lazy, and easily gets jealous. But when there's fun to be had Bloo's the one to have it with.

Mac: Bloo's best friend and his creator. Mac is an eight year old boy with a huge heart, and normally the only voice of reason once Bloo's schemes start. Mac was forced to bring Bloo to Fosters because his mom thought he was too old for him. But as long as Mac visits every day at 3 PM Bloo won't be put up for adoption and Mac can keep him.

Wilt: Wilt is the 10 foot tall basketball playing Imaginary Friend created by BBall superstar Jordan Michaels. Wilt is very apologetic (so much so he'll say he's sorry for anything) and can't seem to say no to anyone's request.

Eduardo: Normally referred to as a big scardy cat, Eduardo was created by Officer Nina Valaroso to protect her as a child from the bully's in her neighborhood. Soon it was obvious that Ed wasn't only there to protect Nina but to help her become stronger by protecting him. Eduardo is a sweet heart and like potato's, he has a imaginary puppy named Chewy.

Coco: Coco is a... Plant, Bird, Plane thingie... That was created by a little girl on a deserted island where her plane crashed, it is unknown where this girl is now. Coco was recovered by two nerds and awhile latter was brought to Fosters. Coco can only speak and spell "coco".

Francis "Frankie" Foster: Frankie is Madame Fosters 22 year-old granddaughter and the one who pretty much makes Fosters run as well as it does. Frankie works at Fosters doing all the chores, despite being stressed out by this most of the time she keeps a smile on her face. The only reason she stays at Fosters is because she loves working with the friends and believes in Foster's purpose.

Mr. Herriman: Herriman is the president of Fosters and the man in charge, he was created by Madame Foster when she was a little girl and she never gave him up. He is very strict with rules and is the bane of Frankie's existence as he's always ordering her around.

Madame Foster: The woman behind it all, she's the one who founded Fosters and made it a place for Imaginary Friends to go once their kid gave them up. Madame Foster is a nice old woman but sometimes it seems she's lost her marbles; such as the time when she used the money in the vault to get the vault gold plated.