21st Century Humo(u)r is the title of an era of comedy, commonly consisting of random sound effects such as the "reverb fart" and "deez nuts". Those born during Generation Z will find this level of humo(u)r highly laughable.
Example of 21st Century Humo(u)r:
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An internet user who is willing to fight in the comments of a YouTube video to prove that they were, in fact, the first to comment on it, demanding to be "pinned".
Person 1: "First! Pin me!"
Person 2: "No, I was first!"
Person 3: "Alright, we all know damn well neither of you were first, now shut up, you pin gremlins."