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
Eren and Mikasa leave for school, bumping into Sasha, Conny, Jean, Christa and Ymir along the way. Upon arrival, they accidentally wander into the Titan's side of the school, where they encounter peril in the form of a rain of titanic school supplies. They are rescued by Hannes, the school janitor, who takes them to the human side and upon the introduction of their teacher, Keith Shadies. At lunch time, the Titans arrive and begin to steal the student's lunches; Eren attempts to fight back by attacking the Colossal Titan, but instead falls from the rooftop and has his cheeseburger stolen.