Two anthropomorphic rabbit twins named Yin and Yang that train under Master Yo, a grumpy old panda who ends up being their father. They learn the sacred art of Woo Foo, a special type of martial arts that involves might and magic. They must work together to save the world from evil villains and forces that want to destroy, corrupt, or take it over. But through all these adventures, Yin and Yang still portray typical siblings; sometimes disagreeing with each other, but still care about each other and working together when needed.
Yin, Yo's student. Yin is a pink rabbit. Yin is often described as intelligent, cute, girly, and sassy. She mostly uses with the Mystic side of Woo Foo, but she can also use the Martial Arts side of Woo Foo. She is often quite stubborn, and shows signs of being a "neat freak". Yin generally has a good sense of right and wrong, and usually does the right thing. It has been shown, mostly in season two, that she likes "bad boys", but she has said it was just a phase. Yin's favorite color is pink, and her favorite animal is a two-ni-corn (a unicorn with two horns instead of one). Yin loves to sing, and is apparently very good at it. She is also a shopaholic. She can also be vain and self-centered at times and not being that nice at all, and really likes evil guys. upon discovering Coop was working for the Night Master, gained an attraction to him. It was because of this personality trait that she temporarily became evil through Coop's influence, and went on a rampage across town with him to prove that she was evil enough to be the Night Mistress (with him as the Night Master). Before she and her brother Yang were adopted by Master Yo they were street urchins or waifs. She is the same age as Yang.
Yang, Yo's student. He is a blue rabbit leader of group woo foo and the twin brother of Yin. He mostly uses the Martial Arts 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, and it is shown that Yang pushed Yin out of the way so Yin would not get in trouble by Master Yo when he appeared in the secret Woo Foo Armory. He enjoys fighting, and likes hitting stuff. His catchphrases are "Hippity hoppity hard", "That's right!", "(Aw) Pellets!", "Whatever!" and "Two words. 'Who' 'Cares'?". He also cares about saving the world. Yang owns a sword which can transform into various objects such as weapons,household materials and fruit. He enjoys video games, likes motorbikes, and also telling jokes. In the current season, he has decided to be a nicer person. Girls are a big part of Yang's life. Lina, his girlfriend, is one of them. Yang doesn't usually think about what is best to use against an enemy before leaping into action. Unlike Yin and Yo, he has not yet turned evil for a short time, which is ironic considering his violent personality compared to them. A group of evil spirits claiming to be "Woo Foo elders" had guided Yang on a quest to find magical items, but it turned out to be a trap to free Eradicus from his eternal prison. However, Yin, Yang and Yo were able to defeat him. Yang's battle cry is "Chee, Hoo, Wha!" .it is revealed that he is an 11-year-old. Before he and his sister Yin were adopted by Master Yo they were street urchins or waifs.