The physical impossibility of turning things into people is something language does with great ease. If you're from Rome you are a Roman, if you do political science you are a political scientist, and if you're into Star Trek, you are a Trekie. All you need is the right suffix and everything is possible. The problem is, what is the right suffix? Here is a selection of the most common candidates.
Perhaps the best place to start is with the character 人 (jin, human). It can be attached to the name of any country or region in the world to refer to a person from that place. Which is very convenient because, unlike in English where you have to choose from a whole catalog of -ese, -ers, -ans and -ians, in Japanese there's only -jin. No matter if you're from Finland (フィンランド人, Finrandojin), from Kansai (関西人, Kansaijin), or from Mars (火星人, Kaseijin), jin will always work.
Other types of people that are defined by the -jin ending are bijin (美人, beauty), rinjin (隣人, neighbor) and rōjin (老人, old man), not to forget fujin (婦人, lady), shujin (主人, husband) and, if applicable, aijin (愛人, lover), among others. The type of person changes slightly when the reading of the character becomes nin. Examples are byōnin (病人, sick person), shōnin (証人, witness), honnin (本人, the person him/herself), and tanin (他人, other person). Note that 人 can also be read as hito — the native Japanese reading — as in koibito (恋人, lover) and tabibito (旅人, traveler).