'OC' stands for original character. An original character is a character that has been created by the writer, and does not appear in the actual book.
Some fanfiction authors create romantic pairings between an original character and a character from the actual book.
Some reviewers may or may not like original characters. It depends on how the original character's storyline fits in with the storyline of the books.
An example of where reviewers may not like original characters is when writers attempt to fit them into the surroundings of the actual books. For example, if an author's original character was given a storyline where they attend Hogwarts from the Harry Potter series, then reviewers may not like the story because it takes the attention away from existing characters.
It depends on how realistic the situations are. In other words, how likely it would be that the event would take place in the books.
Some fanfiction authors create romantic pairings between an original character and a character from the actual book.
Some reviewers may or may not like original characters. It depends on how the original character's storyline fits in with the storyline of the books.
An example of where reviewers may not like original characters is when writers attempt to fit them into the surroundings of the actual books. For example, if an author's original character was given a storyline where they attend Hogwarts from the Harry Potter series, then reviewers may not like the story because it takes the attention away from existing characters.
It depends on how realistic the situations are. In other words, how likely it would be that the event would take place in the books.