Starting School! Titan Junior High School

Nyūgaku! Kyojin Chūgakkō (入学！巨人中学校) is the 1st episode of the 1st season and the 1st episode overall of the Attack on Titan: Junior High anime, produced by Production I.G.

Overview
On the very first day of junior high, Eren oversleeps and is woken up by Mikasa. While rushing to school, he runs into several of his classmates. When they arrive at school, everyone except Eren notices something is odd. They realize that they walk into the Titan side of Titan Junior High, and are introduced to their class 1-4 properly by Hannes. They attend the entrance ceremony, only to find that their principal unleashes Titans to crash their entrance ceremony.

Summary
The giant hand belonging to the Colossal Titan looms over a Wall, with Eren Jaeger and his friends standing behind it in horror. The narrator explains that humanity received a grim reminder of living in fear of the Titans.

It is morning and Eren is woken up by Mikasa for his first day of school. Half-asleep, Eren mumbles that he feels like he had a long dream. Mikasa also points out that he has been drooling. Eren soon realizes that he is going to be late and screams in panic. Mikasa and him hastily run downstairs as Eren stops by to drink his milk, half-dressed in his uniform while their mother wishes them a good day and smiles.

As Eren putting the rest of his uniform, the both of them rush to school. Eren orders Mikasa not to tell anyone about his drooling, in which she agrees... and also utters that she will not tell anyone that he wore his pants backwards. Ashamed of his own doing, Eren runs ahead and pretends not to listen. Along with the hurry, he crashes into Christa Lenz and quickly helps her up. Upon noticing that she dropped her breakfast, Ymir emerges and splits them up. Apologizing, Eren gives her something and rapidly runs off as Ymir shouts angry slurs at them, only for Christa to spot. Eren only gave her a ten yen coin.

Disregarding Mikasa's warning, Eren collides into Sasha Braus, destroying her watermelon breakfast. As another token of apology, Eren gives her a small picture of him and Mikasa but Sasha demands for him to pay for her watermelon. With the hopes of not bumping into someone, Eren collides with Jean Kirschtein. Putting his hurried mindset first, Eren steps over him but as Mikasa does, Jean gets dazzled. Mikasa thinks of a bumping encounter with Eren. With that in mind, she finds a different route and runs at top speed in high hopes to run into Eren. Just before Eren bumps into Conny Springer, Mikasa comes crashing into him and instead sends him flying. Somehow, he ends up right in front of Titan Junior High, with everyone he crashed into before runs up from behind.

The class bell rings and Eren runs the wrong way: to the Titan's side of the school. Eren finds his class 1-4, however Conny points out that the door is far too huge to open. Mikasa finds a smaller door, so they enter class 1-4. A life-size eraser hits Eren on the head as Sasha is uneasy about the classroom. Eren angrily carves his name in the eraser. Mikasa reiterates Sasha's words, but before he can speak up again a triangle ruler impales his head and he frantically runs around screaming. He soon acknowledges that he is being picked up by a Titan through the ruler in his head and slips off. The Titan also picks up the dropped eraser but notices Eren's carved name in it. In a fit of rage it hurls its giant stationery at them, which they dodge in panic. Jean trips over his own feet from running and tries to commit a perverse act (pulling down Christa's skirt), but instead pulls down Conny's pants and they start tumbling out of the classroom. Hannes the janitor finds them and the bunch are relieved.

Hannes laughs at their antics and points out their school building. In class 1-4, Keith Sadies welcomes them. After a short introduction, Sadies proposes the class introduce themselves to each other. Christa starts off and so does Ymir. Annie continues halfheartedly and Reiner Braun follows. Sadies goes to Conny, who salutes with the wrong hand. He gives Conny a noogie and moves on. It is soon Eren's turn and he passionately announces that he will drive out Titans from the entire world. Jean arrogantly calls Eren out and they soon start arguing, however Mikasa breaks up their fight and Jean instantly falls for her. Seeing as Mikasa and Eren already have a sort of relationship, Jean yells that he is jealous of Eren and their fight is stopped by Sadies.

Sasha is caught eating a rice ball in class and Sadies interrogates her. She claims that she elected to eat her rice ball since she couldn't have her watermelon. As an attempted act of kindness, she offers "half" of her rice ball to him. A while later Sasha is being served punishment but is stopped by the school announcement to meet up at the courtyard with lunch. Their headmaster, the Colossal Titan, kicks down the fifty-meter tall Wall. The students run and scream in panic as their lunches are being taken. The Colossal Titan reaches for Eren, who decides to run up to the roof of a nearby building and steal cleaning supplies to retaliate. Despite the cheers of his classmates, Eren takes a high fall and his lunch is stolen nonetheless. The upperclassmen watch the first years from above.

Parodies

 * The opening scene of the episode is a mirror of the opening scene of the first episode of the main anime.
 * When Mikasa wakes Eren up to go school, the scene is a parody of when she wakes him up from the dream he had in episode 1 and chapter 1; although instead of waking up crying he wakes up drooling. He also asks her not to tell anyone about it.
 * Keith's introduction is a parallel of his introduction to the cadets in episode 3.
 * Conny also makes the salute incorrectly like in that episode and is punished as a result.
 * When Eren talks about his intentions of driving all Titans out and Jean mocks him, the scene resembles the moment they met in the aforementioned episode.
 * Just after that, Jean also notices Mikasa and develops a crush on her, complimenting her about her hair, but Mikasa ignores him and goes with Eren; all similar to that episode.
 * As a result, Jean grabs Eren from the collar and gets ready to punch him, openly admitting that he is jealous. This is a parody of a similar scene from episode 4.
 * When Keith catches Sasha eating a rice ball in class, the scene holds many similarities to when he caught her eating a potato in episode 3.
 * The first appearance of the Colossal Titan is very similar to his first appearance in episode 1. It also kicks the Wall and opens a hole, letting the other Titans enter the school.
 * Thomas is eaten by the same Abnormal Titan that ate him in episode 4, although the Titan regurgitates him unharmed and only steals his lunch.
 * The flashback Eren experiences due to the appearance of the Colossal Titan and the way he tries to attack it resemble the second appearance of the Colossal Titan in episode 4.

Trivia

 * When Eren and Mikasa run to school, it can be seen on the TV of the dining room a promo of the first season of the main anime.