Not everything referenced in this is part of a joke or part of popular culture, but the majority is.  Most of the things that show up would be things that somebody in their late teens/early twenties in the UK who dabbles a little in other cultures would be aware of, but I know that most of you aren't my age and aren't from the UK.  Not everybody is going to know what a gat (which features in chapter 21) is, for example, and not everybody has played Pokemon or has watched Game of Thrones, or has read Harry Potter recently enough to remember that the pear needs to be tickled in the fourth book to get into the kitchens.  No matter.  It's all laid out.  If you think something's missing, chances are it's a) in an earlier chapter (as I will only reference it once (the first time it comes up) unless it's something like Leigh's name and the joke is expanded upon later) or b) I've left it out, in which case let me know.  I've also put in explanations for places (such as Hyde Park, which anybody who's lived in London will know, but people who don't live in the UK are unlikely to know) and that sort of thing for anybody who might not be familiar with them.  Basically, if I think there's a chance somebody might not know what something is, what something means, or what's being referred to, I've put it in, whether or not it's part of a joke.

Pretty much everything relating directly to EXO is tagged under "fandom joke/fandom reference" even if it's not a fandom-specific thing.  I didn't feel the need to include ships and pairings (like HunHan) because I think that's one part of K-pop culture that everybody's aware of even if they don't follow K-pop or any specific group too closely.

Some chapters don't/won't have any references.  It just depends on the situation and what I can shoehorn in.  Unfortunately, I'm only human, so if you spot something that's missing, something that's wrong, incorrectly referenced or incorrectly labelled, or something that's in bold when it shouldn't be or not in bold when it should be, please tell me!