As Mai moves to close the hatch of the slurry pipeline, her right thumb is as black as her glove.
Given that the Drill was a metal structure that is driven by a steam engine, why didn't Azula use her lightning to attack everyone? The metal would have conducted and spread out her attack, and given that it runs on steam, it wouldn't have affected the vehicle itself.
When Azula jumps off the edge of the drill, she falls a long way. Azula may be good, but she's not immortal, and that fall should've broken bones.
When Aang is being held against the wall by Azula and about to be blasted by lightning, the camera zooms into his opened eye, which is brown. But in numerous other episodes we see that his eye color is steel gray.
How could Azula possibly stop herself from sliding down the side of the drill? As we see before the slurry is extremely slippery, and she was halfway down when she stopped herself. Moreover, there's no way she could climb up.
When Katara asks Toph to help hold back the slurry as Toph approaches, Toph's pants are already covered in slurry but when she takes her stance to bend the slurry, her pants are suddenly clean before she puts her foot on the ground and dirties her pants.
When Azula is sliding on the top of the drill and crashes into Aang, they both go in different directions down the side of the drill. In the aerial view of them sliding across the top of the drill, Azula is nowhere near the edge, but in the next scene, she is already sliding down.
All the concentration of mud on the pipes, the pressure should have crushed anything inside them, especially when Toph and Katara bend it together. But when Ty Lee is pushed inside and then outside she just seems unharmed.
Katara shouldn't have been able to hold back all that rushing slurry on her own, let alone be able to splash Sokka and still keep it up. That stuff was coming in a rushing torrent, was the length of the entire drill and more was coming, and was mud, which is very heavy. Not to mention she should have been exhausted from cutting through the braces.
When Katara is talking about Ty Lee in the infirmary, she's wearing her necklace, but when she stands up and asks Sokka what's up, her necklace is missing.
Aang: You shouldn't give 100% of your energy into anyone strike. You've gotta be quick and accurate. Hits a series of points, and break your opponent's stance. And when he's reeling back, you deliver the final blow. His own weight becomes his downfall. Literally.
Aang: Everyone inside that wall...the whole world...is counting on us.
Sokka: The whole world minus the Fire Nation, that is.
Jet: What do you think, Longshot?
(Longshot, mute, looks back expressionlessly)
Jet: I can respect that.
Sokka: Toph, Come on!
Toph: No way am I going in that metal monster. I can't bend in there. I'll try to slow it down out here.
Sokka: Okay, good luck.
Customs Lady: So, Mr. Lee, and Mr.....umm Mushy, is it?
Iroh: It's pronounced Moo-shee.
Customs Lady: You telling me how to do my job?
Iroh: Uh, no no no. (speaking charmingly) But may I just say that you're like a flower in bloom, your beauty intoxicating.
Customs Lady: You're pretty easy on the eyes yourself handsome. (makes cat-claw gesture) Raorrr. Welcome to Ba Sing Se.
Zuko: I'm gonna forget I saw that.
General Sung (smiling): It is an honor to welcome you to the outer wall young Avatar, but your help is not needed.
Aang: Not needed?
General Sung (smugly): Not needed. I have the situation under control. I assure you the Fire Nation cannot penetrate this wall. Many have tried to break through it, but none have succeeded.
Toph: What about the Dragon of the West? He got in.
General Sung (startled): Well... uh... technically yes. But he was quickly expunged. (more confidently) Nevertheless, that is why the city is named Ba Sing Se. It's the impenetrable city. They don't call it Na Sing Se. (belly laughs, then becomes serious) That means penetrable city.
Toph: Yeah, thanks for the tour, but we still got the drill problem.
General Sung (pacing back to look out over wastes): Not for long. To stop it, I've sent an elite platoon of earthbenders called the Terra Team.
Sokka (thoughtfully): That's a good group name, very catchy.
Katara: Aang, what are you doing here? I thought you were looking for Appa?
Aang: I was, but something stopped me. Something big.
Wounded Earthbender (About Ty Lee): She hit me with a bunch of quick jabs, I felt like I could barely move. Then she cartwheeled away.
Sokka: Come on, Team Avatar!
Katara: Enough with the Team Avatar already! No matter how many times you say it, it's not going to catch on!
Sokka: Okay, how about the Boomerang Squad? See, it's good, 'cause it's got Aang in it. Boomer-AANG.
Aang: I kinda like that one.
Sokka: Or how about the Aang Gang? Or the Fearsome Foursome.
(Katara starts walking off)
Katara: Forget it, Sokka.
Sokka: What? We're fearsome!
Mai (seeing her teammates covered in slurry after the Drill's been destroyed): We lost.
Iroh: I know there is no use crying over spilled tea... (breaking up) but that's so sad.
Toph: You want the Avatar's help now?
General (meekly): Yes, please.
Ty Lee: Look at that dust cloud, it's so poofy... Poof!
Sokka: Good technique little sister, keep it up! Don't forget to breathe!
Katara: You know, I am just about sick and tired of you telling me what to do all day! You're like a chattering hog-monkey!
Sokka: Just bend the slurry woman!
Zuko (speaking to Iroh through clenched teeth): What are you doing firebending your tea?! For a wise old man, that was a pretty stupid move!
Aang (While cutting metal through waterbending): What I would give to be a metalbender.
Mai (looking at the slurry): Ugh! Disgusting.
Ty Lee: Come on, you heard Azula. We have to follow them.
Mai: She can shoot all the lightning she wants at me... I am not going in that wall-sludge juice.
Aang: So, the question is, how are we going to stop that thing?
Sokka: Why are you all looking at me?
Aang: You're the idea guy.
Sokka: So, I'm the only one who can ever come up with a plan. That's a lot of pressure.
Katara: And, you're also the complaining guy.
Sokka: That part I don't mind.
Ty Lee: Wow, Azula! You were right! It is the Avatar! (smiles at Sokka) And friends...
Sokka: Hey... (Katara drags him away)
General Sung (after the Terra team is taken out): We're doomed!
Aang (to General Sung): Tell your men to stop throwing rocks down here!
General Sung: Men, whatever you do, don't stop throwing rocks down there!
Katara (to Ty Lee): Try and block my Chi now, circus freak!
Sokka: AHH! It's so dark in here! I can't see anything!
Toph (sarcastically): Oh no! What a nightmare!
Sokka: I'm the idea guy, you guys are the chop everything up with waterbending guys. Together, (dramatically pointing one finger into the air) we're Team Avatar!
This episode along with The Serpent's Pass as the TV-Movie: Secret of the Fire Nation.
Character Debut: General Sung
This general is part of the Council of Five, loyal to the Earth King, and is the person in charge of protecting the wall.
This episode is in the Avatar: The Last Airbender Book 2: Earth, Volume 3 DVD, along with The Library, The Serpent's Pass, City of Walls and Secrets, and The Tales of Ba Sing Se.
Director Giancarlo Volpe was nominated for and won the 2007 in the category "Directing in an Animated Television Production" at the 34th Annual Annie Awards for his work on this episode.
For Comcast Digital Cable subscribers, this episode, along with The Serpent's Pass, was available for viewing On Demand beginning September 12, 2006.
The drill conquest could be compared to the Greeks trying to defeat Troy with the Trojan Horse. Both wars lasted a considerable amount of time and both had kingdoms behind a wall.
Once inside the drill, Sokka states that while he was the "idea guy", Aang and Katara were the "chop things up with waterbending guys." This alludes toward the possibility that Katara's name is derived from the word katar, which are Indian arm swords, as Sokka expresses chopping motions with his arms while delivering the statement.
The method for moving the the stone cars of Ba Sing Se's monorail system is similar to that of the locomotion of the stone "cars" on The Flintstones.
The train station where Jet, Smellerbee, Longshot, Zuko, and Iroh came to to go to Ba Sing Se is similar to the Grand Central Station in New York City.
The sheer size and architechture of Ba Sing Se's outer wall is very much similar to that of The Great Wall of China, which was one of the locations Avatar co-creators Mike DiMartino and Bryan Konietzko visited during their trip to China the year before.
"Fearsome Foursome" is seems to be a play on Marvel Comic's Fantastic Four.
Iroh: I know there's no use crying over spilled tea.
This is a reference to the saying "It's no use crying over spilled milk."