fanservice

Short definition from Wiktionary

Noun

1. 1
   Elements added to a television program or similar entertainment that appeal to avid fans but are of little interest to outsiders.
2. 2
   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.
3. 3
   Special interactions from idols to their fans.