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.
YMMV: Drama Drama Duck
Ensemble Darkhorse: Many of the most popular characters are from series you've never heard of in your life.
Fridge Brilliance: The Tokumei Sentai Go Busters cast has adopted Sawatari Makoto, which seems like a strange match at first. However, she fits with them for more reasons than just being extremely odd. As noted on the former canon's page, the Go-Busters all have outstanding weaknesses that are also the weaknesses of computers: freezing, overheating, running out of power, popups, and connection issues. And what's Makoto's weakness (and that of half the cast of Kanon)? Memory problems. The fact that Makoto was picked up from 1999 of all years helps, too.
I Am Not Shazam: It used to be common practice to refer to muns by the name of their most well-known character, rather than by their actual names. However, since chat died and the game moved to Plurk for OOC discussion, this practice has lost popularity.
Memetic Mutation: Far, far too many to count. The most enduring may be "Oh tosh, I'm arriving!", much to all the British players' chagrin.
Sequel Displacement: This game expresses a localized version, where Mobile Suit Gundam 00 has Sequel Displaced the rest of the franchise. Even though it's a very big, very old, and very popular metaseries, and even though DDD's had a Wing cast for ages along with its 00 cast, when Plurk or chat discusses a marathon session of "Gundam", one can almost be assured that 00 is what they mean. The same thing is happening with Macross Frontier.
Sequel Displacement is undoing itself at least in the Gundam scenario, now that there's been a mass enabling of people to watch and app from Wing.
Tear Jerker: Put it this way: almost all of the muns are cruel, cruel people who love causing this. It helps that characters can move through canon as the game goes on, so canon deaths, trauma, and angst can have just as big an effect as they did in their original form or worse.