SM often adds little twists and additions to NCT songs that are almost unrecognizable at first listen but I really appreciate after noticing to the point of obsession, and I will list some examples of this:
Earthquake chorus:
Just before the harmonization of "world" on the first part of the chorus there is another harmonization that is barely noticeable and concur at the same time as the "Hand wave" choreography (0:58) and (1:55).
Hello Future Last chorus/outro:
Whatever is happening on those last 40 seconds is so satisfying to hear, the addition of that synth improves the chorus even more, and those heavy sounds at the end with that final drop that for some reason remind of UFO's which perfectly matches the weird yet happy concept.
I love all of those electronic sounds happening on the chorus going in and out. Also special mention to the 3 chords added on the 2nd prechorus (2:11) and bridge (3:10) that weren't there on the 1st prechorus.
I will keep posting more of these when I feel like it because there are too many examples.