These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Genius Bonus: "What's domain, domain range? / A kid with too much in his pants". In math, domain is expressed by x, while range is expressed by y—the joke here being that said person is "XXY", which is the chromosomal makeup for a hermaphrodite.
He's done this a few times actually. Went from typical musical comedy about being in love with an old person and KKK jokes, to brilliant, layered humor through a bunch of mediums, and seriocomic pieces such as Art is Dead.
Hilarious in Hindsight: In Welcome to YouTube, he says that "most of the best YouTubers are either Asian or they're gay, so there's an untapped YouTube celebrity and his name is George Takei." While he's not so much specifically a YouTube celebrity, but since the song's debut, Takei has gained a huge internet following.