One reason for the widespread popularity of Avatar: The Last Airbender is that the series was able to introduce multiple mystical traditions into a cartoon, in a way that children could understand. The protagonist, Aang, was not just the Avatar, he was also a monk whose pacifism and vegetarianism was rooted in real-world Buddhist traditions.
Chinese, Japanese, Indian and Hermetic spiritual philosophies were explored throughout the show, introduced by older mentor characters such as the guru Pathik and the beloved Uncle Iroh. However, one character who is shockingly wise is Ty Lee -- someone whose physical abilities are admired, but who many fans dismiss as a ditzy flower child.
Ty Lee is introduced in the Season 2 episode, "Return to Omashu," as an old friend of the Fire Nation's Princess Azula. Everything is quite literally upside down on-screen as Azula approaches Ty Lee, who, as part of a circus troupe, stands balanced on her two index fingers, her entire body erect in a graceful gymnast's pose. Recognizing the princess, she spins about, lowering herself into a deep bow of respect. This sets the tone for what fans should expect from her character going forward. When Azula tries to recruit Ty Lee to hunt down Iroh, she respectfully declines, saying how happy she is with the circus and that her "aura has never been pinker." After being coerced to join the princess, who menaced her with wild beasts and fire during a trapeze performance, Ty Lee explains her change of mind: "the universe has given [her] strong hints that it's time for a career change."
These lines of dialogue may seem like New Age buzzwords, but they actually speak to a deeper mystical understanding. While auras are considered a fairly modern concept, popularized in the 19th Century, they can be traced to some of the same Greek Hermeticism that inspired the four elements of the show. They are also connected to the "aureola" halo-like designs painted around holy figures in Vedic and Buddhist art.
In other words, Ty Lee is expressing a state of spiritual fulfillment. Similarly, when she speaks of the universe giving her a message, "the universe" could be meant to express "Dharma" or "Tao," religious concepts which have both universal and personal importance for each person (and whose many complexities would take too long to be discussed here). Her decision to phrase things this way also demonstrates a keen sense of diplomacy.
Throughout the series, Ty Lee has three defining traits: her airy easygoing mirth, natural personability and incredible physical talents with gymnastics and martial arts. This last trait is best exemplified in her ability to block her opponents' chi and even paralyze them by striking key points along their bodies. Every Bending style moves chi differently through the body. As such, Ty Lee's chi-blocking skills demonstrate her own deep knowledge of the flow of chi and the meridians -- which is where it concentrates in the body. In fact, all of her gymnastics have an alchemical yogic quality to them, as spiritually aligned as they are physically graceful.
Finally, one should actually consider her attitude in Avatar: The Last Airbender. Ty Lee's natural instincts with people betoken a deep understanding of others as she is receptive to their needs. She is incredibly diplomatic, managing to spend time around Azula without exacerbating the fire princess's wrath. Ty Lee is not what anyone would consider book smart or street smart, and her youth sets her apart from mentor figures like Iroh. However, she has demonstrated profound spiritual wisdom on par with any other character in the series and deserves to be recognized for it more.