The Science Fiction And Fantasy TV Shows That Had Perfect First Seasons

We take it for granted that TV shows need to take some time to find their feet and get into a groove β€” especially genre shows, where the concepts have to "gel." But some shows manage to come out of the gate strong. What are your picks for the science fiction and fantasy shows that had (nearly) perfect first seasons?

Please include a picture or clip for your chosen show. And please mention the name, and why the first (or in some cases only) season was so perfect. Thanks!

Top image: Firefly, artwork by Tim Doyle. See below for my reasons why.