Well one could assume that most people in this community will recognize both of them since they both come from very popular shows. One of these shows even sits currently on the top of all the time in most anime ranking sites.
Both shows are actually very unique and thought-provoking with little to none fan service. (IMHO this meme wouldn't be so funny if it was about "pervy" shows)
There are no harems and no cat girls, instead we got well written characters and a great story. (Well we got an elf and a wolf but that's not important)
I could say way more why these shows are amazing but I'll just say: go watch them! Both are worth your time.
Both characters get a lot of memes/attention in these kind of communities, so they're expected to be well known if you've been otherwise active here (or in any anime group).
For example, I haven't watched either show, but I know that the green haired girl is Übel from Frieren and the wolf girl is Horo from Spice & Wolf.