chupacabra with an automatic weapon

The author's proudly displayed fetish

The author's fetish you're pretty sure they don't realise they have

The author's fetish which they're firmly convinced everyone has and is just pretending otherwise

The author's non-sexual special interest which just sounds like a fetish because of their habitually unfortunate phrasing

The fetish the author is making a well-meaning effort to cater to in spite of clearly not understanding it themselves

The author's fetish that never quite makes it into the text because they keep getting sidetracked by the requisite worldbuilding

The author's utterly pedestrian sexual preference which the text treats like a bizarre fetish because they've got shit to work through

The author's seemingly innocuous recurring trope they're going to have a personal revelation about ten years down the road