Last night’s “Community,” the first of the series’ fourth season, was also the first made without creator Dan Harmon, the difficult perfectionist who had made it the most ambitious, genre-goofing comedy on TV. Since Harmon got fired last spring, it’s been very hard to imagine “Community” staying “Community” without him. The new episode, despite being a good-faith, fittingly meta-effort, only solidified this: The new iteration of “Community” feels like a zombified one. This got us thinking: What are some other changes, be they a behind the scenes personnel switch, a plot point, or a casting decision, that forever ruined a popular TV show? We took to Twitter to the ask the TV critics who participated in our year-end Blue Glow Awards their opinions (and sparked a great debate about “Moonlighting” in the process.) Here’s what they had to say.