|“||Best imaginary friend ever, eh? He's using a knife for pizza. Sus-*pee*-cious!||„|
Extremely selfish, rude and arrogant, Bloo has noticeably become much more of an antagonist since the start of the series, serving as an antagonist or otherwise acting downright evil in several episodes. However, there are times when Bloo actually feels remorse for any of his actions and apologizes for whatever he's done.
- Store Wars: Steals a cushion from a couch in a store, but mostly kicks people in the shins and calls them rip-off artists. This marks Bloo's first villain role.
- The Trouble with Scribbles: Opening the secret door of Scribbles even though he was told not to.
- World Wide Wabbit: Uploaded embarrassing footage of Mr. Herriman to the Internet.
- Phone Home: Kidnaps a man in a cell phone costume (thinking he was an imaginary friend) and stops him from leaving the house.
- Who Let the Dogs In?: Bloo becomes jealous of puppies who get love and attention. He tries to expose them to Mr. Herriman, who has a fear of dogs, as an attempt to get rid of them.
- Adoptcalypse Now: He and Mac stop imaginary friends from getting adopted, but only because they hate to see their close friends leave them.
- Partying Is Such Sweet Soiree: He attempts to give sugary candy to Mac to make him go crazy.
- The Big Leblooski: Betrays Madam Foster's bowling team just for a paddle ball.
- Where There's a Wilt There's a Way: He forced Wilt to give him more chips, causing Wilt to miss the game.
- Sight for Sore Eyes: He chases a kid thinking he was Ivan's blind owner, Stevie. As a result, he was beaten by his older brother. He then starts chasing after children with pointy hats in a birthday party hoping that Ivan's owner Stevie is one of them.
- Cookie Dough: Bloo helps sell cookies to pay for a new roof. But later turns everyone into servants and forces them to make more cookies as an attempt to become rich.
- Squeakerboxxx: Bloo steals a squeaky elephant from his friends, and accidentally breaks it. He then buys glow-in-the-dark vampire teeth for himself when Mac ordered him to replace it.
- Beat with a Schtick: He told the new guy an offensive joke about his tall height, "How's the weather up there?", causing the new guy to challenge him to a supposed fight. Everyone else bet against Bloo to teach him a lesson. Then at the end, when the new guy explained that he loved Bloo's joke he made a joke of his own, but Bloo thought it was lame causing the new guy to pound him.
- Bye Bye Nerdy: Bloo tries to give Mac a cool makeover to make him less of a nerd, and trained him to be cooler as well, which caused Mac to look more nerdy.
- Bloo Done It: Bloo becomes jealous when a frequently-adopted and beloved imaginary friend, Uncle Pockets, comes to visit. He then tries to demonize him and expose him as a fraud.
- Eddie Monster: Inadvertently causes Eduardo to run away, ridiculing him for his cowardice. However, he later apologized after Eduardo bravely rescued them from Terrence.
- Camp Keep a Good Mac Down: On a camping trip, Bloo eats all the food and puts everyone at risk. He also does the rain dance which extinguishes their only fire.
- Crime After Crime: Bloo tries to get in trouble so he can be sent to his room and avoid eating "It" for dinner. Instead, he gets everyone else punished and sent to their rooms (though Eduardo was actually breaking a rule at the time and Bloo inadvertently exposed him). In the end, he is forced to eat "It" as punishment for his crimes.
- Land of the Flea: For some reason, Bloo becomes jealous of Eduardo's imaginary fleas. He shaves off Eduardo's fur and wears it as a coat, but treats it poorly and almost gets the fleas killed.
- A Lost Claus: Bloo unintentionally ruins Christmas while trying to make sure he gets more than one present, causing him to be on Santa's naughty list, and receiving a pile of coal.
- Cuckoo For Coco Cards: Bloo becomes jealous of the attention that Coco is getting from children, and ends ups scaring them away. He later becomes obsessed with collecting trading cards, and goes as far as annoying his friends to the point of making them give up their cards to him.
- Challenge of the Superfriends: Bloo becomes jealous when Mac hangs out with Imaginary Man, so he joins the forces of evil with NemeSis as "Lord Uniscorn".
- I Only Have Surprise for You: It is revealed that he always surprises Mac on his birthday, much to Mac's disapproval.
- Bus the Two of Us: Bloo takes the Foster's Bus for a spin, getting him and Mac lost in the middle of nowhere, picking up hitchhikers, and getting into a police chase.
- Bloo's the Boss: Bloo thinks that nobody appreciates him, so he leaves and makes up his own home for imaginary friends, which turns out to be made of boxes and filled with puppets and a kitten. He later ruins the chances for an imaginary friend being adopted when he sells the kitten to a family, and tries to steal it back when he misses it.
- Cheese-A-Go-Go: Believed Cheese was an alien, and tried using a Space Observatory Intercom to call aliens to take Cheese away, which is illegal. This may have unintentionally caused the Cartoon Network Invaded Saga, as the aliens misunderstood Bloo, thinking he was saying there was actual cheese on Earth (it is stated in the final chapter of the Cartoon Network Invaded Saga that Bloo, along with Mac, were abducted by the aliens.)
- The Bride to Beat: He inadvertently ruins Mac's cousin's (Tammy) wedding thinking that Mac's getting married.
- Better Off Ed: Started a paintball race and gets in trouble for it at the end.
- Jackie Khones and the Case of the Overdue Library Crook: Selling Mac's name to a DVD club.
- Pranks for Nothing: Bloo disobeys all of Mr. Herriman's rules in the hotel, and Bloo challenges Wilt, Eduardo, and Coco to a prank war.
- The Bloo Superdude and the Great Creator of Everything's Awesome Ceremony of Fun That He's Not Invited To: When he was sick, he gets delirious about being a superhero and gets everyone else sick as a result.
- Bad Dare Day: Exposes to all of Foster's that Mac is in love with Frankie Foster.
- Goodbye to Bloo: In the final episode of the series, Bloo hears that Mac is apparently moving away, so at first he actually plans to kill him. Later he tries to give Mac a great last memory, however he gets disgruntled by him spending time with others. He soon finds out that Mac was just moving into Louise's (Cheese's creator) apartment. This episode shows that Bloo really cares about Mac.
- Bloo is voiced by Keith Ferguson who also voices Marluxia from Kingdom Hearts Chain of Memories and would later voice Hater from Wander Over Yonder, another series created by Craig McCracken.
- Bloo's Japanese voice actor Noriaki Sugiyama also voices Kevin Levin in Ben 10: Ultimate Alien, Sasuke Uchiha in Naruto anime, Buford Van Stomm in Phineas and Ferb and Jason Todd in Batman: Under the Red Hood.