Alternate Company Equivalent: The concept of a rotational Idol Singer group is popular in Japanese Pop Music and has been around for a long time, the oldest being Onyanko Club in the 80s. Also, NCT isn't the first to reference themselves by year — Morning Musume had been renaming themselves by year since 2014 to help fans keep track of who was in the group at the time.
Base-Breaking Character: Taeyong, one of the more popular members even as a trainee, was pretty controversial when NCT was about to debut after allegations of his bad behavior and online scamming in middle school hit the news. There was a faction dismissing his actions due to his age at the time, another faction who claims the allegations are false, and a third faction who were disappointed and believed he should be held responsible.
Face of the Band: Taeyong was heavily promoted even as a trainee and is featured prominently in most of the group's visual videos. He is also the center for the majority of dances in the songs he appears in.
Germans Love David Hasselhoff: NCT Dream is the most popular subunit among Japanese fans, since their concept and music draws similarities to upbeat Japanese Pop Music (especially pop music acts under Johnny's Entertainment like Arashi). Another reason is because most of the hardcore Korean Pop Music fans in Japan are in middle to high school, and all the members of NCT Dream would be around their age.
Yuta was Winwin's roommate when they were trainees and is constantly praising how cute Winwin is. He has introduced himself in one video as "the person who loves Winwin", wrote on his whiteboard that he loves Winwin in Korean, Mandarin Chinese, and English, has said he gets upset when Winwin doesn't watch anime with him during an episode of Nimdle, and has even kissed him on the ear in an episode of their reality show, NCT Life in Osaka.
"And that's a long-ass ride..." (a line from "The 7th Sense")
"Free _______!" (Examples: Free Johnny, Hansol, Kun, even NCT U or hidden rookies such as Jungwoo)
"I lived in America for four years! That's why I'm here, man." Jaehyun's Piss-Take Rap in the English promotional SM Rookies video is constantly referenced in every instance Jaehyun is speaking English.