Generics are the 'extras' of badfic, lacking any personality or description whatsoever. They make loud noises in unison, gather around to watch epic battles (or worse, in the case of "Celebrian"), and ooh and aah over the Sue's battling/dancing/singing abilities. In particularly pathetic cases, they are supposed to be supporting characters, but have no defining traits except for "admiring the Sue" or "loathing the Sue". "Hogwarts Exposed" exceeds all expectations by having even some of the main characters be Generics.
Their mating call is well-known to be "Watermelon, watermelon, cantaloupe, cantaloupe".
See Also
The following may share characteristics with Generics, though usually they are somewhat more defined, except in the case of Random Orcs. Those are only defined by wanting to kill/kidnap the Sue.