noun: (fandom slang) Elements added to a television program or similar entertainment that appeal to avid fans but are of little interest to outsiders.
noun: (fandom slang, chiefly ACG, often derogatory) The inclusion in a work of fiction of material, especially of a racy or sexual nature, which may or may not have relevance to the storyline and is designed merely to excite the viewer.
noun: (fandom slang, idol fandom) Special interactions from idols to their fans.