Cult following

A cult following is a group of fans who are very devoted to a work of culture. It is often called a cult classic. A movie, book, musical artist, television series or video game, among other things, has a cult following when it has a small but very passionate fanbase. A common thing of cult followings is the emotional attachment the fans it. They often say they are part of a community.
Many cult fans express their devotion with a level of irony when describing entertainment that falls under this realm, in that something is so bad, it's good. Sometimes, these cult followings are actually camp followings. Fans may become involved in a subculture of fandom. They may do this either through conventions, online communities or through activities such as writing series-related fiction. They may also make costumes, replica prop and model building, or creating their own audio or video creations from the formats and characters.