Also re: Londo and G'Kar, I cannot get over that in just two conversations in 4x21 the show sells them perfectly as two people who are soulmates in the sense that they become so annoying when interacting with each other that no one else would put up with them. (I suppose they already were this in season one, but in a much more antagonistic way.) I definitely could not have written, would not even have thought to write, that entire conversation they're having - well, mostly Londo is having - about Narn vs Centauri sex in the shuttle bay when Vir walks in.

ETA: And along those lines, it's also really fascinating to see Londo dial it back when he switches from talking to G'Kar to talking to Vir! He's entirely capable of being inappropriate when talking to literally anyone, we've definitely seen that with him at other times, but he's definitely in a different mode when he's talking to G'Kar, at this point in their relationship trajectory, and you can see him become noticeably more toned down with Vir.