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Voiced by: Scott McCordA blue, male rabbit and the twin brother of Yin. He mostly uses the Might side of Woo Foo, but he can also use the Mystic side of Woo Foo. Yang is a cuckoo, lucky, courageous character, and has a liking for clowns. Despite not usually showing it, he really cares about his sister and Master Yo's well-being. He enjoys fighting, and likes hitting stuff.
- Attention Deficit... Ooh, Shiny!: Especially the case in "Brain Drain" where Master Yo grows frustrated with Yang's inability to stay focused; though he ends up being able to use his brain towards the end, he still struggles with this.
- Yang just loves meat (Isn't he a rabbit?) and Yin often exploits this by throwing him a steak just to get him out of the picture.
- Badass Adorable: A cute blue rabbit who is a Woo Foo practitioner.
- Battle Cry: "Chee, Hoo, Waa!"
- Blood Knight: Loves kicking butt.
- Blow You Away: "Foonado!"
- Blue Is Heroic: A blue rabbit and one of the main heroes.
- Book Dumb: He's intelligent in his own way.
- Brains and Brawn: The Brawn to Yin's Brains.
- Brilliant, but Lazy: In "Doomed to Repeat It", he says that he does learn stuff, but he doesn't want Master Yo to know that, so that he could get away with more; in fact, if he is willing to think, he is able to escape traps/situations more often (unless he wanted to be trapped/captured just so he could fight some more).
- Brother–Sister Team: With Yin.
- Bruiser with a Soft Center: "Touchy Feelings" reveals he's this. When his emotions are blasted out of him (takin the shape of small color bunnies of energy half his height), Yin tries to find the Love bunny, since Yang loves to kick butt. While searching for it, the Love bunny approaches behind Ying and Fre-ped. It's practically a Kaiju in terms of size, being almostt twice as tall as the buildings of the city. Yin and the villain lampshade this revelation on much Yang really cares:Fre-Ped: Wow, he sure bottles up that thing deep inside there, doesn't he?Yin: It's a boy thing.
- Butt-Monkey: He suffers a lot because of every other character on the show which includes bad guys (especially Saranoia), his sister often picking on him and his lazy panda guardian neglecting parental duties or worse eating up Yang's bamboo sword. Yang finally gets his revenge on just about everybody in "Deja Foo".
- Calling Your Attacks
- Catch-Phrase: Several. There's "Aw pellets!", "Curse you math!" and "Thinking makes my brain hurt!"
- Chick Magnet: Has gotten the attention of Lina, Melodia, Princess of the Stink Aardvarks and even the dangerous Smoke.
- Crouching Moron, Hidden Badass: Sure he isn't as smart as his sister, but he is still a powerful warrior and capable of surprising feats and even more surprising thoughts.
- Cute Bruiser
- Deadpan Snarker
- The Dog Bites Back: In "Deja Foo", being fed up with the way the world mistreats him (that includes Yin and Yo), when he gets a time loop redo he throws pancakes at Yin's face and frames Yo for ruining a bad guy picnic, before inadvertently getting them killed. He regrets this.
- Dumb and Drummer: In "The Gig is Up", he's the drummer of the band.
- Dumb Muscle: Tends to rely too much on violence to settle his problems even if he does have his moments of clarity.
- Excuse Me While I Multitask: Has shown more than a few times that he's able to make wise cracks and goof off, even engaging in a full conversation with someone without looking at whoever is attacking him.
- Foolish Sibling, Responsible Sibling: Foolish to Yin's Responsible.
- Half-Identical Twins: With Yin.
- Heinz Hybrid: Master Yo is his father, making him and Yin half-panda.
- Hidden Depths:
- He is actually more intelligent than he appears to be and when he puts his mind to it, can be very studious and learn techniques quickly.
- In an episode revolving around mind-reading, we learn he loves writing poetry (usually about Lina) as well as fantasing about painting her toenails.
- I Shall Taunt You: Especially during "Yin-Credible", it's shown that he tends to get the upper hand on foes by teasing them throughout.
- Inter Species Romance: With Lina who turns out to be a dog.
- It's All About Me: Tends to be rather selfish in his actions if he feels he'll achieve some sort of award in the end, but it normally turns out to be a facade to hide his insecurities.
- Jerk with a Heart of Gold: The Heart of Gold aspect becomes more apparent with Character Development.
- Kid-anova: He's a pre-teen yet has gotten the attention of a few females, one of which older than him.
- Large Ham: Befitting his loud fighting style.
- Love at First Sight: Towards Lina.
- Obfuscating Stupidity: Yang is smarter than he initially appears, but he does this so he can get away with things and to make people not to expect anything from him. Actually lampshaded in an episode.
- Official Couple: With Lina.
- Pint-Sized Powerhouse
- Polar Opposite Twins: With Yin.
- Power Glows: His sword glows when it is especially powerful, most likely through charginng it with woo-foo energy.
- Purple Eyes: Which he seems to have inherited from Yo.
- Red Oni, Blue Oni: Red to Yin's blue.
- Sibling Yin-Yang: With Yin, duh.
- Stalker With a Crush: A mild example though it's no longer the case when him and Lina become a couple.
- Sword and Sorcerer: The Sword to Yin's Sorcerer.
- Tsundere: A family-love related version with Yin and Yo, often trying to avoid showing affection or dismissing tender moments with a deadpan "whatever".
- Vitriolic Best Buds: With Roger Jr.
- White Bunny: Colorfully averted.
- Why Did It Have to Be Snakes?: He hates dentists.
- You Gotta Have Blue Hair: Yang is a blue rabbit.
Voiced by: Stephanie MorgensternA pink, female rabbit and the twin sister of Yang. She mostly uses with the Mystic side of Woo Foo, but she is also skilled in Martial Arts. Yin is often described as intelligent, cute, girly, and sassy, but she's often as stubborn as her brother while being a "neat freak" and a "control freak." Yin generally has a good sense of right and wrong, and will often do the right thing.
- Action Girl
- All Girls Like Ponies: Or Twonicorns, as the case may be.
- All Girls Want Bad Boys: She's only hot for Coop when he's evil. She reveals this was a phase and snaps out of it. She hooks up with Coop once he channels his powers for good.
- Attention Whore: Incredibly during "Yin-Credible" where she takes credit for Yang's witty insults just to hog up the spotlight. This ultimately ends up biting her in the butt later.
- There's also the time Yin attracted all the boys around her in "Old School" in her new hot armor and teenage body.
- Badass Adorable
- Badass Bookworm
- Balloon Belly: Briefly in "How The Cookie Crumbles"
- Barrier Warrior: Due to a number of Deflector Shields, she's able to create force fields as a shield or use them as their own weapons.
- Brains and Brawn: The Brains to Yang's Brawn.
- Brother–Sister Team: With Yang.
- Butt-Monkey: Not as bad as Yang but she still suffers for the sake of comedy quite a bit.
- Calling Your Attacks: Yincinerate and Transfoomate are common spells she uses.
- Color-Coded Wizardry: The color of her magic tends to change depending on the spell: it is normally a bright shade of blue while her fire based attacks are a fitting red; when activating her aura, it's always pink.
- Cute Bookworm
- Cute Bruiser
- Deadpan Snarker
- Evil Makeover: During "Gown a Fowl", Yin's appearance becomes more and more dark as Coop's evil nature starts to cling onto her, starting off with simply dark clothes and make up until her fur and aura entirely change.
- Excessive Evil Eyeshadow.: Takes up a sudden fondness for dark and heavy eye make up when Coop's evil corrupts her, as well as the rest of her clothing until the markings give her something similar to the Nightmaster.
- Foolish Sibling, Responsible Sibling: Responsible to Yang's Foolish.
- Girly Bruiser
- Granola Girl
- Half-Identical Twins: With Yang.
- Heinz Hybrid: Master Yo is her father, making her and Yang half-panda.
- Hypocritical Heartwarming: She says that she's the only one who gets to laugh at Yang.
- Inter Species Romance: With Coop (a chicken) and Clamuel (a clam) among others.
- Kung-Fu Wizard: A subtle part of her Character Development. Initially she primarily used magic and no real might abilities, but after the Season 1 finale, she has been seen fighting more physically, combining it with her magic.
- Levitating Lotus Position
- Little Miss Badass
- My Sister Is Off-Limits!: A brother variant: she isn't very supportive about Lina's relationship with Yang, though her reasoning equates to wanting to spend more time with her friend rather than Lina with Yang; as a matter of fact, a flashback showed that Yin convinced Lina to "play hard to get" during an offscreen moment when the two first met Lina.
- Neat Freak: Has been used against her before.
- Official Couple: With Coop.
- Pink Means Feminine
- Pint-Sized Powerhouse
- Playing with Fire: "Yincinerate!"
- Polar Opposite Twins: With Yang.
- Positive Discrimination: Although usually presented as the voice of reason compared to her brother and a bit more moral, she's prone to her own mistakes and being a Butt-Monkey while Yang has some Hidden Depths to keep it more balanced.
- Red Oni, Blue Oni: Blue to Yang's red.
- Rose-Haired Sweetie: Though the "sweetie" part can sometimes be debatable, Yin is a rather nice girl with good intentions if her selfishness doesn't get in the way.
- Sibling Yin-Yang: With Yang, duh.
- Sword and Sorcerer: The Sorcerer to Yang's Sword.
- Taking the Bullet: Jumps in front of the Woo Foo Aura Drain Eradictus originally aims at Yang, ultimately letting herself slowly die in his place.
- White Bunny: Colorfully averted.
- You Gotta Have Blue Hair: She's a pink bunny.
Voiced by: Martin RoachTeacher of Yin and Yang, Yo is a grumpy old panda whose age is unknown though implied to be a centenarian (as he'd missed his 117th high school reunion). Yo has great sage wisdom and is a master in the Woo Foo arts, but is also pretty lazy and prone to lounging around. Master Yo mentors Yin and Yang in the Woo Foo way to save the world, but it wasn't his choice; the spirits of past Woo Foo warriors stopped him from watching a movie called "Who Stole the Cookie" until he decided to do it. He's able to use both might and magic and has moves that Yin and Yang have no clue about.
- Action Dad: He turns out to be the biological father of Yin and Yang.
- Afro Asskicker: Back in his younger days, he dawned skills as broad as his afro.
- Badass Adorable: When he was reverted to a toddler in an episode. Even at three years old, he was already more talented and powerful than Yin and Yang combined. He could already use Woo Foo Aura better than them and even some unique tricks like calling down thunder with Woofoo Lightning. Lampshaded:Yin: He's only 3 and he can Fooportate?!Yang: No wonder he's a Master!
- Badass Grandpa: More than a century old, but till capable of kicking butt.
- Big Eater: The only thing Yo likes to do other than napping is stuffing his mouth.
- Brilliant, but Lazy: He's a master of Woo Foo, but is now perfectly content to lounge around and do nothing.
- Bunny-Ears Lawyer: A goofy, out of shape old man who nonetheless knows very important lessons and can still kick ass.
- Child Prodigy: Look at Badass Adorable above. Considering he mastered skills that Yin and Yang barely even know about at only three, he qualifies.
- Deadpan Snarker
- Dirty Old Man: Attends a macrame gathering with Yin just so he can meet up with single women that are most likely way younger than he is.
- Funny Afro: Sported one back when he was younger though it's entirely withered away as he's aged.
- Grumpy Old Man
- Hero of Another Story: Is currently trading out his past success to be a mentor though he isn't too shabby on his past skills and still contains a lot of his knowledge.
- Hypocrite: In "A Walk in the Woods" he gets mad about Yin and Yang for being lazy staying indoors and surfing the Internet all day while Yo is much lazier than those two as he's always sleeping or forcing the two to do chores for him.
- I Am Big Boned: In Touchy Feelings where he was losing layers of his body and stripped down to bone, he mentions this. He retains this mindset when his flesh returns.
- Inter Species Romance: In relation to the previous trope, Yo should have had a rabbit girlfriend/wife.
- Jerk with a Heart of Gold: A lazy, gluttonous, and rude old panda, but he does care a lot about Yin and Yang, willing to do what he can to protect them.
- Last of His Kind: He's the last panda on earth.
- Luke, I Am Your Father: He's Yin and Yang's missing dad.
- Panda-ing to the Audience
- Papa Wolf: Though he regularly lets Yin and Yang handle their own battles, he's more than willing to stand up for and rush to their aid if he sees they're in need of help. He especially applies to this after the reveal that he's their biological father.
- Parental Substitute: Has practically raised two children due to their absence of their actual parents though it later turns out that he was their father all along and had his memory wiped of that knowledge to train them "without bias and fear."
- Purple Eyes: Which explains where Yang got his from.
- Old Master: A spoofed example.
- Spirit Advisor: Despite he's still alive, his spirit appears to advice Yin and Yang when he's not present.
- Trademark Favorite Food: He loves his soft pretzels.
- Trickster Mentor: He takes some pleasure in letting his students make their mistakes and him rubbing it in their faces regarding his advice.
Voiced by: Novie EdwardsAn aqua-green female dog, Lina is Yang's girlfriend (after "Gone-A-Fowl") and Yin's best friend. She is a nice, yet short-tempered girl who lives on a farm with her father. She was first introduced in "Beetlemania", when Yang pretended to be a Woo Foo Warrior in order to impress her, but his plan backfired after he had to fight a giant steel beetle; eventually, Yin was able to get Yang to tell the truth. Lina is often unafraid to state her opinion and even talks back to her father. She was trained by Yin and Yang to use Woo Foo and is the second-in-command of the Woo Foo army Yin and Yang gathered together.
- Action Girl: She was somewhat this as a civilian. Became a more prominent example once she Took a Level in Badass and learned Woo Foo's Might techniques.
- Blush Sticker
- Birds of a Feather: Her and Yang; while she is often the voice of reason and more level-headed than Yang is, she can also be pretty hot-headed (albeit in a more subdued matter) and some of her dates with Yang show they love to go out and whack gophers.
- Catch-Phrase: "Talk to the hand!"
- Deadpan Snarker
- Furry Female Mane: Has short magenta hair.
- Interspecies Romance: With Yang. She's a dog.
- The Noseless
- Official Couple: With Yang.
- Only Sane Woman: She's this when she has to deal with Yin and Yang arguing.
- Purple Eyes
- Sassy Black Woman: Sure, she's blue but she certainly has the voice and personality of one.
- Spell My Name with an "S": Some people called her Lena.
- Took a Level in Badass: Learns some of the Might techniques of Woo Foo. She's seen using the Paws of Pain a couple of times and one scene in the final battle has her even using a glowing bamboo sword like Yang.
- Tsundere: Lampshaded by Lina herself in "Gone-A-Fowl".
- Violently Protective Girlfriend: Defending Yang from Evil Yin in "Gone-A-Fowl".
- Vocal Evolution: For a short moment, she has a very high voice in "The Truth Hurts" and then goes back to a deeper voice.
- You Gotta Have Blue Hair: You Gotta Have Aquamarine/Turquoise Fur
- Zettai Ryouiki: A Grade B at most.
Voiced by: Damon PapadopoulosLogically the son of Yin and Yang's part-time enemy, Roger the Skelewog. At first, Roger Jr. was a bully to Yin and Yang, having mock fights with Yang and teasing him and Yin, but, during "Woofoogeddon", it was revealed he longed to be Yang's best friend. Roger Jr., being a monster, has displayed super strength, such as when he easily took out a whole group of the Night Master's soldiers just by running by them with his arms. He is also a member of the Woo Foo army Yin and Yang gathered together.
- Breath Weapon: He has the ability to breathe fire.
- Friendly Enemy: At first, Roger Jr. was a bully to Yin and Yang, having mock fights with Yang and teasing him and Yin, but during Woofoogeddon/Who Knows What Evil Lurks, it was revealed he longed to be Yang's best friend. In Season 2, he ultimately ends up be friending Yin and Yang and their other friends.
- Jerkass Façade: He pretends to hate Yang, but he longs to be his friend.
- Nice Hat: His baseball cap.
- Super Strength: Roger Jr. Being a monster, has displayed super strength such as when he easily took a whole group of the Night Master's soldiers just by running by them with his arms.
- Vitriolic Best Buds: With Yang.
Voiced by: Dwayne HillA magical talking tree stump, Dave is a low-life and is considered pathetic by his friends. Many times, Dave is often caught in the crossfire of battles or hurt in some way by friend and/or foe. He's considered whiny, talks nonstop about his family of trees, and is never noticed. As discovered in Stuck, Dave has the ability to communicate with and manipulate non sentient plants. This apparently surpasses that of the other characters. He is now a member of Yin and Yang's Woo Foo army.
- Butt-Monkey: Is constantly deemed annoying and whiny by anyone who meets him, including his group of friends.
- The Chew Toy: Which is saying something given how much slapstick everyone else suffers.
- Green Thumb: Can communicate and manipulate other plants which ends up making him quite powerful.
- Nice Hat: His baseball cap.
- Plant Person: Literally a talking tree stump. He even has a squirrel living in him.
- Purple Eyes
- Took a Level in Badass: Learns about his abilities during "Stuck" and from then on has been able to use to help out.
- Youthful Freckles
Voiced by: Dwayne HillA nerdy chicken who appears to be scared of any threats and has a huge crush on Yin but because she never returned any of his feelings, Coop joined the Night Master in exchange for the promise to have Yin when the world was taken over. He is a minor villain and he is seen with some of the other villains in the Yin, Yang, Yo intro in season 1. Coop gave the impression of incompetence, but in reality, he had powers and abilities rivaling Yin and Yang's; in the end, Coop couldn't bring himself to go through with the Night Master's plans and held him in place so Yin and Yang could destroy him. Eventually, he returns and ends up overwhelmed by the power of the Night Master, temporarily becoming evil before snapping to normal and going off to train and gain control. Upon doing so, he joins the Woo Foo army.
- Abhorrent Admirer: Towards Yin due to his obsessive behavior and general nature that Yin finds more annoying than endearing, no matter how hard the poor guy tries to impress her.
- All Love Is Unrequited: His feelings towards Yin seem like they'll never be returned that is until the ending of the series when Yin seems to return his feelings.
- Inter Species Romance: A chicken who has, occasionally, gotten romantically involved with a rabbit.
- Nerd Glasses
- Official Couple: Later gets the relationship he's been yearning for with Yin.
- Punny Name: A chicken named Coop, as in a chicken coop.
- Single-Target Sexuality: Only shows to have eyes for Yin the entire series...unless you count his strange fondness for corn (though he is a chicken.)
- Stalker With a Crush: To Yin.
- Took a Level in Badass: In his quest to try and win Yin's affection, he trains under the Night Master and quickly becomes as strong as Yin anf Yang. He does furhter still when he absorbs some of the Night Master's power in Season 2 aand learns to control it.
- Super-Powered Evil Side: Due to the Nightmaster's presence infesting him, he can become a super powered and muscular version of himself that comes along whenever he grows agitated. Of course, this nearly corrupts Yin and he disappears for several episodes to control his evil side.
- Verbal Tic: "Buckaw!"
Muffin, The Town President
Voiced by: N/ADescription coming soon.
- Amazing Technicolor Wildlife: He's a green goat.
- Butt-Monkey: He is usually attacked by Carl.
- I Lied: In one episode when he promised Yin and Yang that he'd get them into a hip club.
- It's All About Me: He's a bit egomaniacal, often losing sight of what's moral.
- Jerkass: He cares mostly about his publicity and popularity (although he does care for his cat Puddin Paws), and is even willing to take credit for the deeds Yin and Yang perform in order to attain it.
- Mayor Pain: The mayor of the town and a real jerkass.
- No Name Given: His real name is unknown, as Carl randomly started calling him Muffin the first time he captured him, and everyone else (including the President/Mayor himself) has been using it ever since.
Voiced by: Bill EngvallA Redneckistanian practicing Woo Foo, while being disliked by his teachers, Yin and Yang, as a stupid, smelly hick; however, when he finally gets the time to clean himself up, he reveals himself to be a smart, well-groomed young man. After defeating the Chung Pow Kitties, Jobeaux reveals his knowledge of Yin and Yang's disrespect and returns home to marry and live in a castle of diamond-encrusted grits (which Yin was fantasizing about before they met). He has a pet armadillo named Fuzzy Thunder that hides in his mouth, giving him a hick accent.
- Deep South: He lives in Redneckistan.
- Modest Royalty: Somewhat. Despite being a prince, he's rather casual and doesn't show much interest in changing his traditional ways even when he does take up a married life in a diamond encrusted grit fortress.
- Royals Who Actually Do Something: Takes a very active role in his kingdom and seems to be the most active method of defense.
- Warrior Prince: Yes, it's hard to believe, but he's a prince.
The Boogie Man is a disco-loving green monster that helps Yin and Yang defeat Pondscüm, Zarnot, Fastidious and Mastermind in "Roboticus Maximus". When the two rabbits were looking for a sidekick to boss around, they chose him. Eventually, they put him in charge over them which lead them to a victory. He became part of the Woo-Foo army they gathered.
- Afro Ass Kicker: A Woo Foo knight who sports an afro.
- Cool Shades: A circular, pink pair.
- Disco Dan: Boogeyman is a disco-loving green monster, and has a funky speech that's hard for anyone to understand.
- Early-Bird Cameo: Appears as a minor character in The Howl of the Weenie.
- Funny Afro: A purple afro to be exact.
- Real Men Wear Pink: His entire outfit (sans the belt, glasses, and shoes) is pink.
- The Unintelligible: "This boogety-bites the big bamma-lamma!", among others. Actually protects him against mind-reading as while someone could read his mind, they still can't understand disco.
- You Gotta Have Blue Hair: He has purple hair.
The Night Master
Voiced by: David HemblenBilled as a "Dark Overlord in an Evil Class All By Himself", the Night Master is a very powerful and dangerous foe who was responsible for the near extinction of Woo Foo by eliminating all of the Woo Foo knights except for Master Yo. The Sensei managed to turn Night Master's army to stone and sent him into hiding for a hundred years until he tricked Yin and Yang into using Woo Foo in order to free his army. The Night Master appears to be a demonic sorcerer bat (as such, he hates light) of some description and has a liking for Gothic, ostentatious outfits.
- As Long as There is Evil: It's possible for about anyone to take up the Nightmaster's reign as long as they prove how terrible of a person they are; so, even if the current one dies, there can always be a replacement.
- Bat Out of Hell: Resembles an incredibly tall and thin bat wearing a cloak.
- Big Bad: Season 1.
- The Comically Serious: It's his short temper and serious nature towards most things that make his interactions with more zany characters all the more comical.
- Dark Is Edgy: Easily one of the more deliberately dark villains of the series with little added to his character to make him seem more silly and pitiful.
- Dark Is Evil
- Evil Laugh
- Evil Overlord
- Evil Sorcerer
- Expy: Aku of Samurai Jack.
- The Heavy: The one who started the main source of conflict with Woo Foo being close to nonexistent int the current society and not at all taken seriously by others.
- Knight of Cerebus: Despite some occasionally funny scenes regarding his fashion choices, he's clearly the main cause behind a mass genocide and he's taken in all seriousness whenever he invests in his plans
- Lean and Mean
- Names to Run Away from Really Fast
- Obviously Evil: He's a giant bat who wears a dark cloak and speaks in an eerie voice; also, he prefers looming in the shadows at all times.
- Red and Black and Evil All Over: The marks around his eyes are red and his cloak is black with red underneath.
- Red Eyes, Take Warning: Sometimes they are most noticeable when he's in the dark.
- Surrounded by Idiots: He's pretty smart himself, it's just that his minions tend to be much less intelligent than him and screw up his plans.
- The Trickster: Enough to get Yin and Yang to accidentally free him.
- Weakened by the Light: His main weakness is sunlight which is why he always looms in the darkness to avoid being burned to death.
- Vile Villain, Saccharine Show: A genocidal, power hungry destroyer who now wants to kill two children and their elderly panda mentor and maybe take over the world in the process.
Carl, the Evil Cockroach Wizard
Voiced by: Jamie WatsonCarl, the Evil Cockroach Wizard (who tends to shout out his name as much as possible and always wants to be called Carl the Evil Cockroach Wizard), continuously schemes to defeat Yin, Yang, Master Yo and the power of the Woo Foo with his insecure genius. He also lives with his overbearing mother Edna, who is a dragon (it makes no sense as to how they are all related). Carl is always trying to find a way to impress his mother and out-do his brother Herman. Despite his desire to win his mother's love, Carl is resentful and has talked back (usually under his breath), made her cry, and even put a spell on her.
- Affably Evil: He's pretty friendly with the twins even during evil schemes and the two have allied on occasion.
- All of the Other Reindeer: He's the only major villain left out of Eradicorp. Because the front is a coffee shop, a cockroach running around would hurt business.
- Ambiguously Gay
- Big Bad Wannabe: He actually faces the protagonists far more often per season than the Night Master or Eradicus. He's also a legitimately powerful wizard. It's just that his own foibles and insecurities hold him back.
- Breaking the Fourth Wall
- Card-Carrying Villain: Loves to show off he is evil.
- Catch-Phrase: His full name.
- Deadpan Snarker: Easily one of the more sarcastic characters.
- Disappeared Dad: While seen interacting with his brother and mother, no mention of a father.
- Enemy Mine: One of the only villains to team up with Yin and Yang. He even considered a Heel–Face Turn in one episode but was rejected.
- Evil Is Petty: This is how Yin and Yang get him and Herman to end their truce in Family Day.Yin: We need to get them fighting again... but how?Yang: What's that emotion I have that always makes me wanna dump on your day?Yin: Oh, oh! Petty jealousy?
- Evil Sorcerer
- Green Eyes: Possibly indicative of his jealousy of his brother and/or to invoke Emerald Power.
- Line-of-Sight Name: Carl is really bad at coming up with fake names, he just comes up with "Carla" or "Carlos".
- Not-So-Harmless Villain: He's powerful enough to take out the Night Master's Elite Mooks in droves during the season one finale. He is also the member of the Rogues Gallery that has the most episodes centered around him.
- Lampshahded a few times. Yang points out that while he is dangerous, their insults make him mad and throws him off.
- Another example is where Carl switches minds with Yo. Yo uses Carl's powers to fight back against brother Herman, revealing Carl is as strong as his brother.
- Paper-Thin Disguise: How Yin and Yang never seem to see through them is a mystery, as almost all his plans include the use of a disguise at some point, often more than once an episode, occasionally involving crossdressing, and at least once it wasn't even necessary.Herman: Exactly why do we have to dress like plumbers to sneak into a bathroom window?Carl: You know me, I like to play dress-up.
- Sibling Yin-Yang: With Herman.
- Supernatural Is Purple: His cape is purple.
- Sword and Sorcerer: When cooperating with Herman, with him as Sorcerer.
- The Unfavorite: His mother prefers Herman over him, due to his brother's success.
- Weaksauce Weakness: His weak self-esteem and short temper means that insults throw him off his game pretty easily. Yang exploits this very often.
- Woobie, Destroyer of Worlds: It is implied on numerous occasions that his failed attempts at being a villain efficient and physical abuse of his older brother, is resentment that motivates him to try to defeat Yin and Yang to impress his mother.
Voiced by: Jonathan WilsonA mighty Gryphon who is bent on destroying Woo Foo. As revealed in "Welcome To The Dark Tomorrow", he is in fact the first and original Night Master. After his demise (of unknown cause), other beings of darkness took on the mantle of evil he left behind including an unknown snake lady and the bat-creature Yin and Yang faced in season 1. His deceased minions posed as the ghosts of the Woo Foo Elders to manipulate Yang into collecting the items of power needed to revive him. Tricking Yang into throwing the items into the Night Master's fireplace at the stroke of midnight, Eradicus was instantly resurrected.
- Attack of the 50-Foot Whatever: He's miles taller than about any other person presented, only seeming smaller than the Halloweenie he summons and can stand atop of.
- Big Bad: Season 2.
- Card-Carrying Villain
- Corrupt Corporate Executive: As the head of "Eradicorp"
- Didn't Think This Through: He planned to unleash the Weeniehowl by having it drain people's fears. While this succeeded in creating a large monster that could destroy the city, he also wanted to hear the screams of terrified people (hoping to transform his favorite holiday back into a terrifying affair). However, since the monster completely drained everyone's fears, they had no reason to care what was going on and were completely indifferent to it.
- Early-Bird Cameo: First seen in "Doomed To Repeat It".
- Evil Overlord: The former Night Master.
- Names to Run Away from Really Fast: His name could easily be interpreted as "eradicate", which means to destroy completely; he especially lives up to his name after he successfully brings on the Dark Tomorrow which is the show's equivalent to the apocalypse.
- Large and in Charge
- Large Ham: Lots of it.
- Our Gryphons Are Different
- Power Echoes: Almost always has the presence of two voice speaking at one time, though it's especially noticeable whenever he shouts.
- Suddenly SHOUTING!: To add onto his hamminess, he has a bizarre habit of starting off his sentences in a flat and calm tone until randomly shouting at the top of his lungs by the end.
- Villains Out Shopping: Aside from being evil, he loves polka and to throw slumber parties with his minions
Voiced by: Linda BallantyneA female villain who can read minds. She is the smartest one of Eradicus's minions, though her blunt corrections often get her zapped by Eradicus. Eradicus also forced her into tuba lessons, and can play polka music.
- Dark Action Girl
- The Dark Chick
- Deadpan Snarker: Normally in response to the other's incompetence.
- Evil Genius: The smartest out of the group and is far more likely to plan ahead and approach situations with common sense before jumping head of herself.
- Fiery Redhead: Mostly averted as she's easily the most level headed member of the team and a brunette, but does have a tendency to become incredibly malicious and loud if angered.
- Fingerless Hands
- Flight: Is one of few characters shown to have this ability.
- Magic Staff: Regularly holds a long staff with a glowing red orb at the top.
- Mini Dress Of Power
- Psychic Powers: Is able to mind read and levitate items and harbors a great deal of power from being within her own mind as shown in Mind Games when she nearly overpowers Yin.
- Proud Beauty: Holds a lot of satisfaction in her attractiveness and doesn't take it well when Yin thinks she's not that hot.
- Punny Name: Sounds like "elemental".
- Vain Sorceress: Less magic and more psychic powers, but still fits.
- Women Are Wiser: Consistently the most level-headed and sensible member of Eradicus's organization.
Voiced by: Tony DanielsA villain who has nearly impenetrable armor and can bowl over nearly anyone. He can be best described as unintelligent.
- Affably Evil: Generally pleasant and friendly to everyone due to his stupidity.
- The Brute: An indestructible being who can deflect attacks, roll over enemies and send his enemies flying through the air with one punch or kick.
- Dumb Muscle: Emphasis on dumb.
- Nigh-Invulnerability: Hence his name.
- Punny Name
- Third-Person Person: He refers to himself as "Bob".
Voiced by: Peter CrugoA villain who can stretch himself into any shape and any person. He loves cracking bad jokes. His name is a portmanteau of the gag toys Rubber Chicken and Rubber Ducky.
- Beard of Evil: The only one among his teammates with a beard and is a mook of the Season 2's Big Bad.
- Nice Hat: What appears to be a helmet.
- Pungeon Master: He has a knack for telling bad jokes.
- Punny Name: His name is a play on "rubber ducky".
- Rubber Man: A being made entirely of rubber and thus the ability to stretch.
- Voluntary Shapeshifter: Thanks to being a Rubber Man, he has the ability to contort himself into any shape he wants.
Voiced by: David BerniA villain who can shapeshift and regenerate his limbs.
- The Ahnold
- Brother Chuck: Introduced physically in "Welcome to the Dark Tomorrow" but never seen again.
- Flight: He has the ability to levitate.
- Good Thing You Can Heal: He has the ability to regenerate his limbs.
- Punny Name: His name is a play on "molecular".
- Voluntary Shapeshifter: He possesses the ability to shape shift.
- What Happened to the Mouse?: Mollecu-Lars fled after Eradicus was destroyed in "Welcome To The Dark Tomorrow", and his current status, alive or deceased, remains unclear.
Voiced by: David BerniCarl's black-hearted, sadistic, selfish and evil ant brother, Herman, is a tyrannical ant warrior who rules his kingdom with an iron fist, a diabolical mind, and impeccable table manners. He is also quite the mama's boy. He attempted to take over the world until Master Yo stopped him.
- Aloof Big Brother: To Carl. Though it's never outright stated that he is the elder of the two, it's implied here and there, and he certainly fits the trope.
- Big Brother Bully
- Disappeared Dad
- Drop the Hammer: When he's not wielding a sword or his fists, he uses a warhammer.
- Evil Overlord
- Eviler Than Thou: To Carl.
- A Father to His Men: Subverted. "Please, soldier, don't cry... because weakness is a punishable offense! THROW HIM IN THE DUNGEON!!!"
- Faux Affably Evil
- Gray Eyes
- Momma's Boy: A trait he and his brother share.
- Multi-Armed and Dangerous: He has four arms, making him capable of Quadruple Wielding.
- Multi-Melee Master: Swords and hammers.
- Oh, Crap!: When he finds out that the potion to take away his allergies no longer works because all the potion did was conjure up a clothespin over his nose, and Yin flicked it away easily.
- Satellite Character: While Carl appears plenty of times without him, it's noteworthy that he never appears in an episode without Carl making at least a cameo, if not sharing the spotlight. His character is largely defined by comparison with his brother. It's particularly jarring since he's mentioned as having conquered most of the world, and is played up as being a more competent villain overall.
- Sibling Yin-Yang: With Carl.
- Super Strength: His four arms pack a surprising amount of wallop.
- Strong Ants: His troops aren't pushovers exactly either.
- Sword and Sorcerer: The Sword (or Hammer, or Fists) when paired with Carl.
- Weaksauce Weakness: He's allergic to panda fur. [[spoilers:Both physically and mentally allergic to it.]]
Voiced by: Tony DanielsUltimoose is the ultimate Night Master lackey: tough as nails, a master at Moose fighting, and really, really dumb, despite his shortness and strong antlers. He seems to offer work under the Night Master but is merely a dim-witted pawn.
- All of the Other Reindeer: "Deja Foo" sees the various villains hold a picnic scavenger hunt. Guess who wasn't invited.
- Battle Cry: "HOOH!HAAH!HOOH!"
- Boisterous Bruiser
- From Nobody to Nightmare: In "Deja Foo" after becoming the Night Master, (calling himself the Night Mooster) and killing Yin and Yo and nearly killing Yang as well.
- Harmless Villain: He's treated as one, but can be quite dangerous.
- Large Ham: He tends to be over-dramatic, especially when it comes to manliness.
- Moose Are Idiots: A Dumb Muscle antagonist who happens to be a moose.
- Red Eyes, Take Warning
- Straw Misogynist: Ultimoose says a lot of sexist things about women. He is to Yin what Saranoia is to Yang.
- Third-Person Person
Voiced by: Scott McCordYuck, a turquoise-green rabbit with terrible hygiene, is an entity formed from Yin's obsession with control and Yang's aggression. As a disgusting, mutant rabbit, Yuck wants more than anything in the world to be the greatest, most powerful Woo Foo Knight of all time.
- All Your Powers Combined: He has all of Yin and Yang's abilities
- Arrogant Woo Foo Guy
- Ax-Crazy: Aggressive as he is, Yuck seems to derive sadistic fun from generally hurting people and many of his deranged smiles imply he isn't entirely right in the head.
- Badass Adorable: Despite his arrogance and cruelty, he does prove to be one of the most formidable foes in the series, able to outsmart and near victory a number of times by himself. Not to mention that he's possibly the most power Woo Foo knight in existence, nearly killing Master Yo the first time in a mostly one sided fight.
- Big Eater: Eats an entire pie and a pizza in his debut episode in just a few bites, normally making a mess along the way.
- Blood Knight: Having Yang's aggression, this is a given.
- Blow You Away: "Yuck-i-cane!"
- Calling Your Attacks: Sometimes
- Control Freak: Obtains an obsessively controlling personality on behalf of Yin.
- Energy Ball: Is able to devise a ginormous sphere of green energy on one finger strong enough implode an entire town.
- Evil Counterpart: To both Yin and Yang.
- Fangs Are Evil
- Good Costume Switch: In "Upstanding Yuck" he wears a non ripped shirt, seems to have bathed himself, and slicks back his fur.
- Heel–Face Revolving Door: Also in "Upstanding Yuck" he becomes a good guy by having a group of hooded figures beat goodness into him. Yin and Yang don't trust him of course and follow him around, ambushing him whenever his words sound like a threat. They're proven wrong in the end, realizing too late that Yuck was good all along and that their actions have only turned him back to his old ways.
- Hermaphrodite: Though he is addressed using male pronouns, "Yin Yang Yuck!" shows him coming out of a bathroom labeled with a question mark. Then "Personality Problem" reveals that he actually does have a male and female aspect of his personality.
- Hiccup Hijinks: The main thing that defeats him at the end of "Imperfect Fooplicates". Despite his incredibly increased power after inhaling a number of Fooplicate flakes, this also gave him a bad case of hiccups that make him lose control of his abilities and ultimately beat himself up.
- Killer Rabbit: An almost literal version.
- Large Ham: Not quite as much as other examples as he seems to be able to keep his speaking patterns more casual, but he can certainly bring up the ham whenever he makes an entrance.
- Yeah baby, I'm back!
- Magic Knight: Dual-wields the Might and Magic capabilities of Woo-Foo.
- Made of Evil: Made from the negative qualities of Yin and Yang (specifically bossiness/need for control and impatience/violent streak).
- Manipulative Bastard: Has proved himself capable of plotting multiple people to his schemes.
- Master of Disguise: Unlike other villains, he wears some pretty convincing disguises to the point his reveal can be the biggest shocker, normally involving robot suits or someone else's body he'll posses.
- Never My Fault: Rarely ever takes the blame for his failures, especially in "Personality Problem" where he blames Yin and Yang for being on top of their game for him being defeated and towards the end of the episode where he claims his girl half's idea is the reason he lost.
- The Pig Pen
- Pint-Sized Powerhouse
- Playing with Fire: Is capable of doing the Fists of Fire when he's first made, just to prove how powerful he already was.
- Sickly Green Glow: His magic is this color.
- Slasher Smile
- Smug Super: Always feels the need to point out how he's a Level 5 Woo Foo Warrior and he's still hungry for more power.
- Third-Person Person: On occasion, he'll end a threat with his own name, such as shouting phrases like "So swears Yuck!" or "You'll be no match for Yuck!".
- Vocal Evolution: His voice starts off as more nasally in the first season and sounds more raspy in "Voyage to The Center of Yo". In the second season, he has his official voice which is deeper and slightly raspy.
Voiced by: Linda BallantyneA hyper-active female who was, supposedly, Yang's girlfriend. It turns out she was using him to fight against her brother, who in turn, captures Yin to fight against Smoke. Yin and Yang eventually capture the two into Smoke's Prison Prism.
- Affectionate Parody: Smoke and Mirrors capture Yin and Yang and force them to fight in a style similar to Pokemon while the characters themselves are one of anime. Smoke dating Yang is a parody of Pokemon's usual Power of Friendship theme. She is dressed in Sailor Fuku and wields a large Buster Sword-like blade.
- Smoke loses the Pokemon angle in later appearances, becoming an entirely different parody that's only more ironic considering her VA (see below).
- Amazing Technicolor Population: Yellow skin.
- Ambiguously Human: Resembles a human more than anyone else, only excluding her yellow skin and lack of a nose, though she's never specifically stated to be one.
- Ax-Crazy: A number of the things she randomly yells between her lectures range from bizarre to downright terrifying threats towards people who may be annoying her.
- Boobs of Steel
- Cute Little Fangs: Has two sharp teeth that come out of her mouth.
- Dark Action Girl
- Dating Catwoman: Yang dated her.
- Evil Redhead
- Fiery Redhead: Can't go very long without screaming a threat, normally finishing with a giggle.
- Impossible Hourglass Figure
- Large Ham
- Magic Skirt: Despite doing a great deal of fighting, her skirt stays in place as though it were cloaked in starch.
- Noblewoman's Laugh: A subtle case as her laughs aren't much beyond a giggle though she always holds her hand up to her mouth whenever doing so.
- The Noseless
- Punny Name
- Rapunzel Hair: That is one HUGE ponytail.
- Red Eyes, Take Warning
- Sailor Fuku: Going along with an embodiment of anime parodies.
- Verbal Tic: Normally finishes her statements with a "tee hee!"
Voiced by: Jonathan WilsonSmoke's rivaled brother. When Smoke uses Yang in the tournament, Mirrors obtains Yin to fight her. Yin and Yang managed to use one of the Forever Friend Prisms to imprison Smoke and Mirrors. Mirrors' hairstyle resembles the hairstyle of Goku from Dragon Ball Z. He appears to speak in a way mocking most anime, by stopping and starting at odd intervals.
- Affectionate Parody: Smoke and Mirrors capture Yin and Yang and force them to fight in a style similar to Pokemon while the characters themselves are one of anime. Mirrors mimics Tuxedo Mask while having a vague resemblance to Goku.
- Amazing Technicolor Population: Green skin.
- Ambiguously Human: Bares a humanized appearance much like his sister's though it's never clarified what he actually is.
- Anime Hair
- Cute Little Fangs: A lot like Smoke's.
- I Know Karate: As he very well points out with a series of poses before disappearing in his introduction.
- Punny Name
- Something About a Rose: Flings one into the ground before his introduction, copying a particular anime.
- Walking Shirtless Scene
Voiced by: Linda BallantyneWith an outfit & magic wand for every occasion, Saranoia is a powerful sorceress and mistress of disguise. Deeply sexist and obsessed with female rights, she is determined to free Yin from studying Woo Foo and take in as her disciple. She had a terrible childhood and always thinks men are like her lazy brother Mark and her boy-favoring wizard father, who she mistakes Yo as, just as she mistakes Yang for Mark.
- Amazing Technicolor Population: Light purple skin.
- Bad Boss: Often yells at and abuses G.P., her gnome assistant.
- Beauty Mark: Under her left eye.
- Demoted to Extra: In Season 2.
- Does Not Like Men: Believes that all men, whether good or not, are all bad.
- Evil Sorceress
- Flanderization: Her Psycho Misandrist traits become her singular trait after her later appearances and she becomes more insane over the course of the series.
- French Maid: In "Bad Nanny Jamma", she tries to get into the dojo this way. However, the given wand forces her to clean every mess before she can even try to get Yang.
- Green Eyes
- Hot Witch
- Impossible Hourglass Figure
- Magic Wand: Has a wide assortment, each of which based on a household objects. Besides allowing her to shapeshift into a certain form (along with her gnome minion), it lends her appropriate abilities. For example, a lipgloss wand turns her (and her gnome minion) into a tween while the broom wand gives her a French maid outfit (along with turning Fred into a poodle.) The wand also influences her magic, as she could only use the broom wand to clean (at least until there was nothing left to clean), which the twins exploited.
- Pirate: In "The High She-as" (fake beard included).
- Squick: In-Universe, her obsession with Yin. Though it becomes saddening when one understands she actually believes she is helping Yin and trying to prevent her going through the same abuse she went through as a young girl despite Yin actually choosing to study magic instead of being forced.
- The Unfavorite: Her father preferred her brother, brainwashed her to study magic against her will and gave her a hatred of men so deep she became homicidal.
- You Gotta Have Blue Hair: Has purple hair.
Voiced by: Jamie WatsonOnce Yang's favorite toy, Zarnot is an evil action figure brought to life by the Lie Fairy, hell bent on destroying Yang.
- Brought to You by the Letter "S": He has a stylized "Z" around his chest area.
- Card-Carrying Villain: He wants to be one.
- Crazy Jealous Guy: A platonic version. It has been revealed in "Dummy Up" that Zarnot still desires Yang's affection and attention, and seems to grow insane jealousies towards any other toy that Yang might be playing with (such as Yochop). Whenver Yang ignores him, he seems to want Yang's attention more, and is willing to go far lengths to attain it.
- Dark Is Evil: His main color scheme are dark blue and black.
- Evil Is Hammy: He uses the same villain cliches.
- Humongous Mecha: Subverted for most of the time, but sometimes displays the ability to grow huge
- Living Toys: The evil type. He's like a Decepticon knock-off with the personality of Talking Tina.
Voiced by: Jonathan WilsonA street, Swedish, fish inside a robot suit. His being a "Swedish fish" appears to be a reference to Swedish Fish candy. He is obsessed with "bling-bling", and will get it at all costs; however, he truly carries a Swedish accent.
- Disco Dan: Loves to disco dance.
- Funny Foreigner: A Swedish fish who loves disco.
- Gold Makes Everything Shiny: Pondscum even wears a gold made suit. He is obsessed with "bling-bling", and will get it at all costs. Even his sidekicks are equipped with gold armor when a battle gets serious.
- Insistent Terminology: Insists that people pronounce the U with the umlaut in his name properly.
- Light Is Not Good: He wears shiny gold, but is a definite antagonist.
- Negative Continuity: He was revealed to be a frog in "Deja Foo", but in "Welcome to the Dark Tomorrow" was a fish again.
- Sidekick: The Blixens.
Chung Pow Kitties
Are little, furry and adorable kittens (at first glance), but they are really evil and heartless ninjas. They usually wear dresses red, blue and green.
- Badass Adorable: As evil as they are, you can't deny their adorable nature or skill in martial arts.
- Cats Are Mean
- Evil Divas
- Expys: Of both Hello Kitty and The Powerpuff Girls, but as villanous pop-star ninjas.
- Pint-Sized Powerhouse: They're small kittens, but they pack a punch.
- Terrible Trio: A trio of cats who commit crimes.
- The Unintelligible: They only say "meow" yet they manage to be an incredibly popular band.
- Took a Level in Badass: They manage to learn something akin to the Woofoo Aura technique; the trio of kitties combine their auras to make an energy cat known as the "CP Kougar."
- Villain with Good Publicity: Due to being a popular band, they're easily able to deceive people and get away with their schemes.
Voiced by: Tony DanielsA gargoyle who is about a "bazillion" years old, Kraggler used to be a great and powerful warrior and Master Yo's arch enemy. Reduced to a feeble old man, after he broke the time traveling hour glass he got the power to drain the youth from anything, or give his age to anything.
- Arch-Enemy: Was one to Yo back in his glory days.
- Grumpy Old Man: He's default form if he isn't much younger.
- Our Gargoyles Rock
- Plot-Relevant Age-Up: Does this to Yin and Yang which later turns into Rapid Aging for the duo.
- Senior Sleep Cycle: Downplayed at best.
- Time Master: The hourglass he had can influence time travel and grants him the ability to influence one's age.
- Totally Radical: Whenever he's in the form of his younger self.
Voiced by: Peter CrugoAn evil mittens-wearing wizard who was a big threat years ago; now he's just a brain looking for a body to regain his reign of evil.
- Diabolical Mastermind: Mastermind is power hungry, and wishes to gain full domination of the planet as he did in the past.
- The Ditz: "I was the ruler of an empire that covered over twelve continents in a world that only had seven!"
- Evil Brit: He has a British accent and is a Diabolical Mastermind.
- Green and Mean: He emits green flames and is one of show's antagonists.
- Hair-Trigger Temper: He also has a short temper, which results that his head is engulfed in green flames which are usually extinguished by emergency water sprinklers.
- Was Once a Man: He was once a human wizard.
Voiced by: Seth MacFarlaneA half-man with hairy hooves, but all man (that is if one would count collecting comic books and action figures manly). He is a large man with a bald head who dresses like a city man.
- Ambiguously Bi or Camp Straight: He's trying to win over Womanotaur and he has an interesting fashion sense.
- Bald of Evil: He's bald and his plan was to kidnap all the Twonicorns and to shave off all their hair to make a large wig to cover up his really smooth, bald head to get a date with the Womanotaur.
- Evil Lawyer Joke: Becomes on in "Game Over".
- Four-Fingered Hands: Unlike the rest of the cast, he subverts it. Most of the cast treat it as a horrifying thing that he has five fingers.
- Half-Human Hybrid: Half man, half minotaur.
- Large Ham
- Real Men Wear Pink: He's not ashamed of wearing a pink shirt or sweater.