Audience-Alienating Era: Town Jr., from the late 90's. The sets were mind-bogglingly simple to build, with buildings made of a few specialized "juniorized" parts, cars with single-piece chassis, printed-on headlights and no doors, and uninspired designs. Thankfully the juniorization has mostly stopped after LEGO realized its mistakes.
Chase McCain only appeared in two sets (not counting the promotional polybag and his LEGO Dimensions Fun Pack), but he's usually the main selling point of both because of his home game.
The rescue helicopter set, for as small as it is (literally just being that of a helicopter and 3 minifigurines—not even a heli pad or station), handily achieved this status after them memes hit.
Memetic Mutation: "HEY!"note The 2010's LEGO City advertisements always have a scene where the minifigures notice an important part of the advertised set's construction, such as a vehicle, is disassembled and shouts "HEY!".
Periphery Demographic: AFOLsnote Adult Fans of LEGO. After all, it's them who can afford the really big and fancy sets.
The 2024 "City Space" sets abandon all pretense of being based on real space vehicles in favor of sci-fi designs, and introduce color-coded spacesuits for the minifigs, essentially becoming a sneaky Futuron revival.
The reaction of many AFOLs upon the color changes that happened in the mid-2000s, in particular the gray colors becoming more bluish and brown becoming more reddish.
Very old-school LEGO fans (or former LEGO fans and parents of LEGO-playing kids) think this way about specialized parts.