Generally speaking, when artists get told something of theirs reminds other people of something else, we don't normally take it as a compliment, even when it's meant to. A lot of times, though, we feel like people are saying we "stole" a character or aspects of a characters, etc, so... yeah. I get a little frustrated when I hear that my story sounds like another story, haha. I know, there are no new ideas in the world, etc etc, but I always feel a little bummed all the same. Everyone wishes they were original, I guess.
I have no idea what you are talking about with the cars, though! But I stopped watching after the first season because I didn't really like that season's characters. Korra was kind of neat, and I would have liked her more if I had been watching the show as a kid, but I didn't like the supporting cast nearly as much as the original Airbender series, and I thought the ending to season one was absolutely terrible. I did like SOME of the series, but the ending was a bit of a cop-out ("Aww, you lost your powers... psyche! Here you go, here are your powers again! Just kidding, you all win!"). But oh well. I really liked the first series, but I didn't like the pseudo-steampunk setting. I did really like cameos from the original characters, though, haha.