I think it's because it's so different and it takes risks. Plus it's really smart humor. It gives the audience credit in terms of not needing to tell them when to laugh. I love that about the show. There's no laugh track.
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The script was just the best I'd read in a long time and I love the humor which I wasn't expecting and I like the fact that my six year old daughter can see the show without being you know protected from it.