The Crossroads of Destiny is the 20th episode and the last episode of season 2 of The Amazing World of Gumball and Aang.
Azula betrays Long Feng and assumes leadership of the Dai Li. While Team Avatar attempts to stop her, Zuko, after some deliberation over the consequences of his actions, betrays his uncle's trust and chooses to attack the Avatar. Aang is fatally injured by Azula while in the Avatar State, but Iroh intervenes and gives his friends enough time to escape. With the Earth King overthrown, Ba Sing Se falls to the Fire Nation. Katara uses the spirit water to heal Aang and he survives. Meanwhile, 'Gumball and Darwin unknowingly become accomplices in the robbery of a convenience store.
It's Nicole's birthday and Gumball, Darwin, and Anais get her presents, but Richard forgot to get one for her. He can't buy a gift for her because he needs to watch the kids.
Sokka and Aang both hurrying back to Elmore on Appa; as they fly along, they spot Toph, who is earthsurfing towards the Watterson's House as quickly as she can. They pick her up and fly to Elmore, trying to get there quickly to see whether Katara is in danger or not for in the previous episode, Aang had a vision that she was in trouble. When asked if he has mastered the Avatar State, Aang lies to the others, saying he has.
Meanwhile, deep underground, Azula — who has been control of the Dai Li by Long Feng for the planned coup — works quickly to establish her position of leadership and make them fear and obey her. She tells them all that soon the Earth King will lock them away, just as he did to Long Feng. This inspirational fear is shown later on when one of the agents visits Long Feng and, when asked about Azula, says that she is both terrifying and inspirational.
Then Richard sends the boys to the gas station. They pick out a holographic card that has a person on it, angry and normal. A robber comes in and scares the cashier with an old, rusty spoon, he then raids the cash register. Gumball and Darwin are about to pay for the card when the robber sees them. The robber then lies to them, saying he wants them to collect something for the Bald People charity, Gumball and Darwin find lots of stuff, including shampoo, which they think is a perfect gift for Bald People. As Gumball gets the shampoo from the bottom of the pile, the the pile falls and reveals a safe.
Iroh and Zuko arrive at the Watterson's House, on the esteem invitation they received to serve him tea. They enter in, Iroh tells Zuko he need to give a time to himself to make some tea, After Iroh deliver some tea, the two become somewhat apprehensive. A circle of Dai Li agents surround Iroh and Zuko, and it soon is revealed to be a plot by Azula. Zuko takes a defensive stance; however, Iroh takes a different approach. He calmly asks Azula if she ever heard why he earned the nickname, "Dragon of the West", to which Azula just waves him off and says she has no time for lengthy anecdotes. However, instead of a verbal narrative, Iroh sips his cup of tea and suddenly begins to breathe fire, attacking the Dai Li agents surrounding him and Zuko. The two begin their escape, dodging projectiles of earth fired by the Dai Li. Iroh destroys a wall with a blast of lightning and leaps out of the palace, landing on the ground and urging Zuko to escape with him. However, Zuko decides to quit running away from his sister and turns to fight Azula. Iroh is clearly displeased at Zuko's decision, but quickly gets up and flees the scene. Zuko challenges Azula to an Agni Kai to which she rejects. He attempts to attack her, but Dai Li agents soon capture and arrest him.
Meanwhile, the gang arrives the palace and confronts Gumball, who assures them that nothing is amiss: Katara is fine, and after the meeting with the Council of Five, she decided to go with the Kyoshi Warriors. They are unaware, however, that the warriors are actually Azula, Ty Lee, and Maiin disguise. When the team goes to their house, they find it empty and they realize Katara is indeed in danger.
As the gang comes to Watterson's House, Toph senses someone at the door. She identifies the person as an old friends of hers, Iroh, and invites him in much to the surprise of Aang and Sokka. He tells them that Azula has captured Zuko, and he pleads with them to help rescue him. Sokka grows defensive; however, after Aang puts the whole image into perspective, Sokka changes his mind and the gang heads outside. Once there, they trap the captured Dai Li agent caught by Iroh in a pinch of rocks, and after Sokka's questioning, the gang learn that Katara is being held in a secret underground cave known as the Crystal Catacombs.
Katara stands in a dark, crystal-lighted cave when suddenly a light shows above. The entrance opens and Zuko is thrown into the cave. As he comes to, Katara takes a defensive stance. Initially furious to see him, she tells him that all he cares about is capturing the Avatar, and how spreading war and hatred is in his blood. When she says that he does not know the pain of the Fire Nation killing her mother, Zuko apologizes, and says that this is something they both have in common, softening her slowly.
Outside the Watteson's House, the gang discovers that there is indeed a huge underground city. They decide that Toph and Sokka should go to warn Gumball about the robber, and Iroh and Aang go to rescue Katara and Zuko. Traveling down a tunnel to the prison, Aang mentions that Toph says Iroh gives great advice and tea. The Avatar also tells the former General of the events with meeting Guru Pathik. When Aang questions his choice, and says how he doubts his abilities without the Avatar State, Iroh suggests that Aang was very wise to choose happiness and love over power and perfection, which are both overrated in Iroh's opinion.
Soon the police man comes and looks around, he is trying to eat a snack when he comes in, but he is a donut and it goes through the hole in him, which happens to be his mouth. Gumball and Darwin find him a snack, which ironically is a donut, he drives off after that. The boys try to open the safe to no avail, until the safe says they just have to say please.
Outside of the Watterson's House, Sokka and Toph soon see General How, but before they can say anything, the Dai Li place him under house arrest. At that same moment, every general in the Council of Five is arrested. The two make it into the Living Room, and they reveal to Richard that the Kyoshi Warriors are not genuine. Upon seeing Sokka, Ty Lee starts to flirt with him, but he says that he is involved with Suki. Ty Lee does not know who Suki is, which exposes them, and Toph throws her to the side with some rocks. Mai, realizing that their identities are now known, throws a hail of ornate shurikens at Toph, who blocks them with a wall of earth. Ty Lee begins to "fight" Sokka, commenting it's like they are dancing as he dodges her strikes. However, the fighting is in vain, as Azula soon has the king at flamepoint. Sokka and Toph surrender, and are disabled by Ty Lee.
Long Feng appears and immediately orders the Dai Li to arrest Azula; however, to his shock, they do not comply. Azula happily explains the situation to Long Feng; the Dai Li don't know which of them is more powerful and who will take the throne. She correctly guesses that he is lower class by birth, but had managed to get his power through incredible work all his life by conniving and trickery; however, she declares that she has "divine right to rule", and confidently takes the Earth King's throne. Long Feng surrenders, bowing to Azula, admitting that she had beaten him at his own game.
Down below in their prison, Katara apologizes to Zuko for how she yelled at him, and tells him that for a long time, whenever she saw the face of the enemy, she saw Zuko's face. He turns away, touching his scar, assuming she was referencing his scar, a mark he feels once symbolized his banishment, and his "destiny" of chasing the Avatar forever. However, he has gained Katara's trust to the point where she offers to heal his scar using the water from the Spirit Oasis. However, before she can do anything, Aang and Iroh show up, both of them embracing Katara and Zuko, respectively.
Zuko and Aang exchange glares, and Zuko grows angry that Iroh was with the Avatar. Iroh sends Katara and Aang off to help Sokka and Toph. Iroh then explains to Zuko that he is a different and changed man, stronger and wiser than ever before. He tells Zuko that he is time for him to choose good. Before Zuko can reply, a mass of crystals springs up and entraps Iroh, and Azula and a couple Dai Li agents emerge from the shadows. She says that she expected this sort of treachery from Iroh, but not from her brother. She feeds him tales of how this is the most glorious day in Fire Nation history, and that if he joins her, Zuko will gain back his father's love and honor. Iroh begs Zuko to not listen to Azula, telling him that the kind of redemption Azula is offering is not the redemption for him, but Azula continues to plot, telling Zuko how she has planned everything, and that they will only win if he joins her. Iroh begs even more, for Zuko to look deep inside his heart and see what he truly wants. Azula sends the Dai Li away, and tells Zuko that he can chose whatever he wants, and she walks away, leaving him to ponder the two sides of the coin.
Meanwhile, Nicole comes home from work and notices that the boys aren't there, she asks Richard where they are and he tells them. Nicole then tells him to put his pants on (which she is always telling him) and then the family goes to the gas station to get them.
Azula catches up to Aang and Katara rushing to save Toph and Sokka from their imprisonment and fires a bolt of fire at them. A battle ensues between Aang, Katara, and Azula, and just as Aang and Katara have her cornered, Zuko shows up. After a brief moment of dramatic tension, Zuko begins fighting on Azula's side, to everyone's amazement. In the midst of the battle, the two pairs switch off, with Zuko fighting Katara, both using element whips on opposite sides of a river. Katara expresses her angry disappointment in Zuko, how she thought he had changed. He replies inscrutably, "I have changed." Aang and Azula charge at one another, Azula sends a blast of fire, sending Aang soaring into the air.
Meanwhile, Toph, Sokka, and the Earth King escape from their cell through Toph's ingenious metalbending. Back at the palace, Ty Lee and Mai have been tasked with guarding the king's pet bear. Mai is lounging, bored, on the steps to the throne while Ty Lee amuses herself, trying to teach Bosco how to walk on his front legs. In an instant both her hands and feet are bound to the floor by Toph's earthbending, and she and Sokka prepare to take on Mai. Mai in her nonchalance just says to take the bear and the king reunites happily with his pet.
When they are there the robber ties them up and tapes their mouths shut. Gumball and Darwin see them and ask why they are tied up. Then, they see the robber and realize he doesn't work for charity and start running. Richard swallows the tape and crawls around, and finds a hot dog on the floor and licks it. Nicole then finds some ice cream and puts it on her rope, Richard bites through it and Nicole goes to save the boys.When they are there the robber ties them up and tapes their mouths shut. Gumball and Darwin see them and ask why they are tied up. Then, they see the robber and realize he doesn't work for charity and start running. Richard swallows the tape and crawls around, and finds a hot dog on the floor and licks it. Nicole then finds some ice cream and puts it on her rope, Richard bites through it and Nicole goes to save the boys.
Underground, the fight continues on, with Katara taking on both Zuko and Azula, but she is knocked out when Zuko and Azula both firebend and slammed into crystal rock, before Aang manages to stand back up from being thrown earlier. He slams into the ground, creating a tidal wave of earth barreling towards Azula and Zuko, but he is stopped by the Dai Li. Soon they are joined by dozens of Dai Li agents, and Katara assumes the octopus stance - water shaped like octopus tentacles. Horribly outmatched, Aang realizes there is no other choice and does the only thing he can think of—creating a quick crystal shelter with earthbending, he meditates, and decides to try to release his attachment to Katara in order to enter the Avatar State. He then rises into the air, but before he can let go of Katara and gain control of the Avatar State, Azula shoots him down with a lightning bolt to the back. At that moment, the Avatar Spirit falls from the plane of existence. As Aang falls back to the ground, Katara creates a huge wave through waterbending, and manages to scatter the Dai Li; Zuko; and Azula, and catch him before he hits the ground. Holding him in tears, she is defenseless, but Iroh suddenly appears. He tells the two to escape, and that he will hold off Azula and the others as long as he can. Once they escape, Iroh surrenders himself to the Dai Li and glances at Zuko, quickly turning his head in shame.
Gumball and Darwin crash into the wall, and the robber takes their bag. Nicole then find them and picks up the bag and a hot dog. The Donut Police Man comes back and sees Nicole with the bag, Darwin and Gumball unconscious, and the cashier tied up. Nicole then gets arrested after the officer sees what happened there
The entire group manages to escape and while flying away on Appa, Katara uses her Spirit Oasis water to heal Aang, who initially appears dead. With a quick flash of light, nothing occurs, and Katara begins to cry and holds Aang close. Then Aang's tattoos glow shortly and he opens his eyes and smiles at her. Overwhelmed and relieved that he is okay, Katara embraces him closer.
Meanwhile, in the Watterson's House Zuko frets over betraying Iroh. However, Azula reassures him by telling him that it was actually his uncle that betrayed them, not the other way around. Zuko then asks Azula about returning to the Fire Nation, raising his doubts about being accepted and having his honor restored since he does not have the Avatar. Azula again reassures him by saying that he has restored his own honor, though Zuko still seems unsure. Azula is firmly in control of the city.
Later, Richard, Gumball, Darwin, and Anais go to the jail and gave Nicole a cake for her birthday. Then, the police man comes in with the real robber, and says Nicole is free to go, but he needs 5 minutes to fill out her paperwork. "5 minutes is all I need", Nicole says, leaving the robber very worried.
The Gang reach the Jail and finding Nicole is Arrested, Katara says to Nicole that Aang is injuried in his back, Nicole calls the hospital to help Aang, In the Hospital. the doctors says it is a scar and can't be healed but they say Aang is okay. Gumball and his family is flying with appa, Sokka says "The Earth Kingdom has fallen".