Both Avatar: The Last Airbender and sequel series The Legend Of Korra have some of the most memorable characters in modern fantasy. While one of the greatest things about following the journeys the characters undergo in any story is seeing how they change, a good first impression can't be undervalued.
So, looking across both series, fans have enjoyed a lot of really great scenes used to introduce new characters; the most exciting, the most atmospheric, and the most revelatory of those introductions are still fondly remembered even long after both series have ended.
10 Aang
In Avatar premiere "The Boy In The Iceberg," the titular character of the series is introduced when Katara and Sokka's squabbling unearths his icy tomb. After Katara then smashes open the iceberg with her brother's boomerang, the awakened Aang stumbles and looks upon his liberator's face like he's seen an angel.
Then, he says his first words in a hundred years: "Will you go penguin-sledding with me?" Those seven words are Aang in a nutshell: He may be the chosen one, but he's also a normal, rambunctious kid.
9 Zuko
As Katara frees Aang, the crack in the iceberg sends a beam of light shooting into the sky. From there, the scene cuts to a metal ship and the series' antagonist makes his debut: Prince Zuko, looking to the horizon in hopes his journey to capture the Avatar is finally at an end.
While Zuko changes the most of any Avatar character, this first scene does establish his essential characteristics— he's determined, short-fused, and has little patience for his uncle's eccentricities.
8 Roku
After a brief glimpse of Roku's commemorative statue in "The Southern Air Temple," Aang's predecessor appears directly in the eponymous back half of the two-part episode "The Winter Solstice." Appearing before Aang in the Spirit World, the previous Avatar warns the current one about Sozin's Comet and the tight deadline Aang is on to master the four elements. Once the exposition is wrapped, Roku manifests in the physical world through Aang and drives off Zhao's Fire Nation troops.
Roku's introduction is a watershed moment for the show; his presence brings gravitas, the information he imparts ups the stakes, and his Fire Nation lineage shows that a nation's evil doesn't preclude its individual members from being good.
7 Toph
Introducing new characters to an established ensemble is risky, but it paid dividends with Toph, who elevated the show and group dynamic with her presence. When the Gaang attends an Earthbending competition in hopes of finding Aang a teacher, they witness "The Blind Bandit" trash-talk then clobber her opponent The Boulder— or, as Toph calls him, The Pebble— to preserve her reigning title as champion.
The scene is a microcosm of the subversion at the heart of Toph's character; the "sassy bruiser" archetype filled by a small 12 year old girl, and a blind one at that.
6 Ozai
The Fire Lord's face is concealed by flames and darkness during the first two Books of Avatar, building him up as a monstrous, inhuman figure. It's only in the Book 3 premiere, when Zuko is at last welcomed back home and he greets the father who scarred and banished him, that viewers see Ozai face-to-face.
As the Fire Lord rises from his throne of flames, the frame then cuts to a close-up of his face. Finally, the shape of the enemy is revealed— not a shadow from a child’s nightmare or a demon born of fire, but a normal, even pleasant-looking man. After all, the deadliest wolves are those cloaked in the wool of sheep.
5 Kyoshi
In "Avatar Day," Aang's past life Avatar, Kyoshi, is accused of having killed a village's founder, Chin the Great, some 400 years ago. Manifesting much like Roku once did, Kyoshi reveals the truth: She did kill Chin, for he was a horrible tyrant spreading fear across the Earth Kingdom and attempting to conquer Kyoshi's native land.
Thus, using the Avatar State and mastery of all four elements, she turned her homeland into an island, leaving Chin to fall from the newly created cliff to a watery grave. The scene is a taste of the power the Avatar State holds, and establishes Kyoshi as a sterner, more pragmatic Avatar than Aang.
4 Korra
After Tenzin's opening narration in The Legend Of Korra's pilot reveals that the Avatar cycle has begun anew, the episode opens in the Southern Water Tribe. Three White Lotus members enter a house, summoned to determine the identity of the new Avatar, and Korra is in turn called by her mother.
From there, Korra smashes through a wall and enthusiastically bends the three elements which she's already mastered. Though a comedy beat, the scene immediately tells us the difference between Korra and Aang. Aang was so desperate for a normal childhood he ran away to find it. No angst about the weight of her duties for Korra, though; she's the Avatar, and everyone is just going to have to deal with it.
3 Zaheer
The Legend Of Korra's strongest villain also had easily the best first impression. Korra Book 3 revealed in its premiere that the Harmonic Convergence in Book 2 had gifted random people with Airbending. Zaheer's debut, the concluding scene of said premiere, showed this was going to cause complications for Korra and her friends.
Imprisoned by the White Lotus, Zaheer offers his captors some philosophical musings about change (Book 3's central theme) before using his new abilities to free himself and imprison the guards in the cell that once held him. Promising the end of the Avatar is at hand, Zaheer departs, viewers having been given a taste of both his literacy and lethality but doubtlessly wanting more.
2 Koh The Face Stealer
Just before Aang enters Koh The Face Stealer's domain in search of the information, he witnesses a monkey devoid of its face, giving viewers a taste of the danger Aang is in once he journeys a few feet farther. Koh stays in the shadows for a moment, before jumping in front of Aang to reveal his enormous, centipede-like body. Circling the young Avatar, swapping his faces and jolting in Aang's own face in hopes of stealing it.
While Aang avoids having his own face stolen, Koh promises they'll meet again. Though his parting promise of a return appears unfulfilled, a creepy realization hits: Koh wasn't speaking to Aang, but the Avatar itself, for his menace is eternal.
1 Azula
Seen twice in brief cameos during Book 1, Azula's proper introduction in the Book 2 premiere can't be beat. When informed by the captain of her personal vessel that the tides will force them to alter their course, Azula asks the captain if the tides command her ship. He answers in the negative. She thus asks him if the tides would think twice about smashing him against the shore if she has him thrown overboard. His answer is the same. Azula's pointed conclusion? "Then maybe you should worry less about the tides, who've already made up their mind about killing you, and worry more about me, who's still mulling it over."
Unlike her brother or Admiral Zhao, the Fire Nation Princess isn't going to be hampered by angst or incompetence. Ruthless, cunning, and driven, it's obvious that the Gaang is in for a boatload of trouble once their paths cross with Azula's.