Kelly and Erin have come a long way from when they were Kelly and Kelly, and Kelly Kapoor was trying to get with Charles Minor.
There's some great deleted scenes from the episode with Jim and Pam in Puerto Rico where everyone assumes that Erin hates Pam, but it seems like she actually idolizes her. In another deleted scene she accidentally destroyed Pam's painting of the DM building when she was cleaning it, and then had to trade her necklace (which she reveals has instructions for when she has a seizure on it) to Kelly so that Kelly will fix it. And then Kelly adds a sun and a rainbow to it. We'll have to see if that makes it into on-screen continuity.
Pam and Erin had that face off last week over the candy as well. They must have either done that scene perfectly or horribly, because they've managed to divide the viewership into two camps. Either Erin was needling Pam over her old territory, or Erin is actually a shockingly good employee in this wacky environment who actually respects and appreciates her boss.
Speaking of Abed (since there's no new Community thread yet), please tell me I wasn't the only one that nearly died laughing for about half the episode while Abed did his SPOT ON impersonation of Christian Bale's Batman. I mean seriously, my girlfriend was yelling at me to stop laughing (over her own laughter!) because we couldn't hear any of the lines starting from his initial appearance all the way through the whole gang crashing the faculty Halloween party. I love this guy!