Rip-off

A cheap imitation of a story without the requisite credit given to the original author.

Many badfics are said to be a rip-off of trite romance novels, canons other than their own, popular songs, and even other fanfics.

Rip-offs are not limited to fanfiction, however. There are many canon works that are considered to be a rip-off of other, superior creations. The Icewind Dale Trilogy, for instance, has many moments in which it rips off Lord of the Rings, while Eragon is reportedly a rip-off of half the high fantasy books in existence, as well as Star Wars.