WARNING: The following contains spoilers for All of Us Are Dead Episode 2 now streaming on Netflix.
The viral outbreak quickly takes off in Episode 2 of All of Us Are Dead and the highly aggressive zombies are definitely reminiscent of a popular 2016 Korean zombie film. While finding brief safety in one of the classrooms, some of the surviving students are trying to make sense of the situation when Lee Cheong-San cleverly references Train to Busan. His friends quickly gawk at the idea that they could be seeing the start of a zombie apocalypse and tell Cheong-San that he watches "too much TV."
Cheong-San doubles down on the reference because the zombies are fast and incredibly fierce in a similar manner as those featured in Train to Busan. He encourages his friends to look out the classroom window for themselves and, unfortunately for Cheong-San's friends, he hit the nail right on the head. The reality settles in as they look out the classroom window in horror and then quickly have to save fellow classmates Lee Su-hyeok and Choi Nam-Ra from being attacked. Su-hyeok, barely breathing, confirms Cheong-San's suspicion as he collapses to the floor while saying "Zombies" and the adrenaline-fueled undead soon come crashing at the door.
The reference and subsequent exchange are a fun way of establishing zombie films as canon in the All of Us Are Dead world while also playing off the trope of "pop-culture and tv will rot your brain." Cheong-San is definitely valid in his reference and it is the perfect analogy for the students' current situation as the violent and agile horde hunt them throughout the halls of the Hyosan High School. The surviving students learn that the local police don't watch a lot of TV either as Cheong-San references the film again and pleads to the police to come to the rescue, but the officers mock Cheong-San's zombie claims and hang up the phone.
As Episode 2 progresses, however, and the outbreak escalates it becomes abundantly clear that people should probably be like Cheong-San and watch more zombie movies. This is especially true for the local police as their laughter soon fades when a surging wave of zombie-related calls hits their telephone lines immediately after they brushed off the young zombie buff. Thankfully Cheong-San's classmates toss their doubts aside in order to come together and hold their own against the insatiable undead mob. They will definitely need to freshen up on their zombie film knowledge though if they want to survive this new nightmare. Or maybe next time they could just listen to Cheong-San.