I recently finished re-watching season two of Buffy the Vampire Slayer, and - spoiler alert - it was just as good as the first one. While the over-arching plot was interesting, the characters (especially the new ones) were what really helped make this season shine.
Spike and Drusilla
Easily one of the greatest evil couples of all time, Spike and Dru roar onto the scene in episode three and attempt to wreck havoc. They're a couple of scene-stealers, and it's always exciting to see their names pop up as guest stars. I was genuinely shocked (and disappointed) when I found out that James Marsters doesn't actually have an accent because it's so realistic (to me, anyway). And you can't deny that Dru (Juliet Landau) is fabulously insane in the best way possible.
Normal broody Angel (David Boreanaz) is nice and everything, but evil soulless Angelus is awesome. After one night of passion with Buffy, Angel loses his soul (and crisp white shirt) and becomes Angelus, he of the bloodlust and leather pants. It's one of the reasons why Buffy and Angel's love story is so tragic - just when they're more in love than ever, Buffy finds herself faced with the awful choice: kill her boyfriend or stand by as he murders everyone she cares about (even if I didn't like Jenny Calendar).
Willow gets a love interest in this season as we're introduced to Oz (Seth Green), who plays in a band and is also - spoiler alert - a werewolf. It's hard not to love Oz - he isn't phased by much (PHASED. You get it? BECAUSE HE'S A WEREWOLF) and takes the supernatural in stride. But he's devoted to Willow and is always willing to help out the Scooby Gang. If Buffy was a YA novel, I'd be hardcore shipping Willow/Oz and hoping for a spin-off series - they're so underrated and (sorry not sorry) I don't like Tara in the later seasons.