fan service n. a feature, inside joke, or obscure reference included in entertainment primarily to please a core fan group, or a work of entertainment expressly created for that purpose; (hence) in anime and manga, visuals which include nude or semi-nude figures. (source: Double-Tongued Dictionary)
Further reading
In 1916, a small-town newspaper in Pennsylvania printed a fanciful item about a local gathering with a guest list that included, among others, Miss Ella Vader, Mr. Ray Zor, and other punny names. This is part of a complete episode. Transcript of...
Matt in Beloit, Wisconsin, reports that when he was in high school back in the 1990s, he and his friends used the word biscuit in phrases like I feel like a biscuit or I bet you feel like a biscuit now, the idea being that someone said something...