TV series have a lot of trouble with consistency unless they have a tight team of in-house writers who are all on the same page. Freelancers with incomplete ba

TV series have a lot of trouble with consistency unless they have a tight team of in-house writers who are all on the same page. Freelancers with incomplete background information or people who disagree on various points cause inconsistencies. And sometimes they just happen under the best of circumstances. In non-geek genres, most people don't much notice inconsistencies, whether they're pedantic things like "someone goes the wrong way to get to his bedroom" or bigger things like, "When did this character become afraid of dogs? He had a Great Dane back in first season!" ETA: Try trawling the TV Tropes wiki for eight zillion examples of how TV writers of contemporary sitcoms and dramas can't even be consistent with the real world the stories are set in. :)