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.
Growing the Beard: Literally. As soon as Freddie shows back up in Lime Grove with a beard and a nicer suit in episode one of the second season, the show seems revitalized.
Harsher in Hindsight: Early in Season Two, Lix tells Randall to stay calm when she tells him bad news, and not to start rearranging his desk. At the time, this is a bit of Lix's typical Deadpan Snarkery about his Super OCD, but when they find out that their daughter (who they've never seen and Randall spent years trying to track down,) died in an air raid we see that Randall does in fact try to cope with extreme stress by rearranging his desk, and it's not funny. At all.
Freddie and Hector. They spend a lot of time staring jealously at each other and sniping over Bel. Plus all of 1.03 and Hector showing off at the hunt for Freddie.
Hector and Laurie in Season Two. They used to be in the army together, and Laurie is apparently very accustomed to putting drunk, handsy Hector to bed. There's also a ton of tension when Laurie participates in the debate on the Wolfenden Report; it's almost as if Hector is angrier at him for hiding his own possible homosexuality and still carrying out the law than the deal with Kiki.
Jerkass Woobie: Hector. The idiot brings most of his trouble upon himself, but one does feel bad for him.
Before Ben Whishaw got famous, it was common for fans of The Wire to tune in for Dominic West.
Season Two also garnered a number of fans of The Thick of It due to Peter Capaldi. The series itself also received a large influx of people discovering it for the first time when Capaldi was named the new Doctor.
Les Yay: Lix Storm confuses everyone's sexuality, but she and Bel seem especially close. They change clothing in front of each other, borrow each other's clothes despite having vastly different body types, and Lix calls her by more pet names than anyone else ("darling", "sweetheart", "munchkin").
Moral Event Horizon: Cilenti crosses it when he has Pike kill Rosa Maria for talking to the team.
Ship Mates: It's not hard to ship Lix/Randall and Hector/Marnie if you already ship Freddie/Bel, since they're all canon pairings and the pairings that the show ends on. If you ship Lix/Freddie, though, you tend to root for the Bel/Hector affair to continue.