sidequel
n.— «Sidequel (Side Story)—A sidequel is a neologism describing a work of fiction in literature, film, and other creative works that is produced after a completed work, set in the same “universe,” with arbitrary chronology and unrelated plots. The word is a portmanteau formed from side-, as in side by side, and sequel, a work which takes place after a previous one. The term may well be synonymous with Spin-off.» —“The Big Screen Bulletin 12.04.06: Jingle Your Bells With The Bulletin” by Chad Webb 411mania.com Dec. 4, 2006. (source: Double-Tongued Dictionary)