Yin & Yang

Yin- 501 (voiced by Frank Welker) and Yang-502 (voiced by Frank Welker) are both of Dr. Jumba's Experiments.

Primary Function
Yin: can absorb water into her head through her tentacles, and then release the stored water in powerful sprays when she wishes. Her tentacles are also used for draining water, gardening and firefighting.

Yang: can fire balls of lava from the spouts on his back at targets and enemies, and heat the ground or other land with his feet.

It is also shown that when Yin and Yang combine their powers, they are able to create rock/land.

Weakness
Yin: If Yin does not have any stored water or access to a water source, she will be rendered harmless.

Yang: Anti-heat foam can incapacitate Yang and render him defenseless.

Trivia

 * Both of they're names is derived from the concept of Yin and Yang; in this case her name stems from the force of Yin, which represents femininity, water and cold, fitting her nature.
 * Yin is a female and Yang is a male.