I'm personally of the opinion that the show's been going downhill even before Harmon left/was kicked out during season 3. Minus a few standout episodes it was mostly parody-of-the-week. Hey, remember when this show took place in a community college with actual characters instead of vague caricatures throwing in tons of nerdy references minus the Big Bang Theory laugh track? Man, those were the days.
As for this episode with the InspectiCon, the funniest part was probably at the end ("BOW BEFORE THORAXIS"). I'm looking more to the Parks & Rec hour-long special after this.