These obvious characteristics are typically called stereotypes. In literature, characters who are designed according to these "obvious" characteristics are called stock characters (given they are based upon stereotypes and, therefore, easily recognized).
Outside of literature, the media plays on stereotypes as well. Commercials are cast based upon the products (females typically staring in commercials for cleaning products and men staring in automotive commercials). Sitcoms tend to work in the same way. Many sitcoms create characters who the audience can identify with or easily characterize (think Steve Urkel from "Family Matters," Doug Heffernan from "King of Queens," and even the blatant Token from "South Park").
It seems that people are far more comfortable when they can readily identify a person, or character, based upon preexisting ideas about the person or character. If the known about the character opposes a person's prior knowledge, then the person will fail to "buy into" what is being shown. Essentially, the disjoint can cause a person to dislike the character or product based upon the fact that it alienates the person's prior knowledge.