A spin-off is a edit of another Flipnote. It can range from minor edits to being unrecognizable compared to the original.
A spin-off normally consists of the audio being intact, with new characters and animations being in place of the old ones. Some creators believe that any spin-offs on their own work is "stolen." Unless a user reuploads an unedited version of a Flipnote, they are not stealing another's work.