I have twin 5-yo daughters and have bought only the space-themed LEGO sets for them. They've seen the "Friends" sets but really just want to build spaceships, airplanes, and cars. I guess I'm doing something right :)

I also have to admit that one of the reasons I bought the space sets was in case they didn't like LEGOs. That way at least I could have some fun with them. Now I have to share...