My first reaction was to the Firefly universe itself: Enough planets that even fully terraformed planets could be forgotten… Asteroids that smugglers could walk around on without spacesuits… cartography unaffected by orbital mechanics so that one planet is always just the other side of the Reavers from another planet… “Hey,it’s Rocket Robin Hood’s universe!”
My first reaction was to the writing: When JMS was producing Babylon 5 and Crusade, he was posting stories about the process and experience to Usenet. For Crusade the suits back at the studio headquarters kept sending him stupid demands. More violence - “We want this episode to start with a fist fight.” More sex - “This main character - we want him to be a sexual explorer and have sex with every alien race he encounters.” A big reason it was cancelled was that he fought many of the dumber demands.
With Firefly it seems like Joss Whedon took every sleazy studio demand for violence and sex, made them work, and made them work WELL. One can see sleazy studio execs demanding “We want this character to be a prostitute. With the occasional lesbian encounter.” And Whedon simply nods, writes it in, and adds a lot of humor.