Lina is an aquamarine female dog (formally believed to be a bear until Yin Yang You!) whom is Yang's crush and Yin's best friend. She lives on a farm with her father. She is an intelligent, pretty, yet short-tempered and sassy farm girl first introduced in "Beetlemania" where Yang lied about being a Woo Foo Warrior to impress her, but his plan backfired after he had to fight a giant steel beetle; however, Yin was able to get Yang to tell the truth.
In "The Yin of Yang", she shows slight feelings for Yang after he tried to act like Yin in order to impress her. In "Smoke and Mirrors" she actually tried to pursue him, though she was constantly interrupted by both Yin and Yang. As of "Gone-A-Fowl", she and Yang exchange their secret feelings for each other and Lina began pursuing a relationship.
She is now a part of Yin and Yang's Woo Foo Army as the second-in-command, though she is still marked as a Woo Foo Knight in a Little Less Training. Lina's species was unknown until the episode "Yin Yang You", which reveals that she is a dog.