It was invented and popularized at a hotel in Tijuana.

Here's a much better one: mandatory melted cheese in their fruit salad (due to their criminal misuse of pineapple)

On the gammon with pineapple thing - I remember a popular science programme when I was young (Tomorrow's World maybe) about gammon and pineapple. It started with a story from the Second World War about some soldiers in the Pacific theatre, who were stranded in occupied territory, and survived by coming out at night and stealing pineapples from the fields. Apparently all their teeth fell out, and this was not because the sugar in the pineapples had simply rotted their teeth as the soldiers initially thought, but because of enzymes in the pineapples softening their gums. And it is these enzymes that soften meat and make pineapple a great meat tenderiser, and hence a great accompaniment for gammon.

There’s also a Mexican taco with pineapple as a topping, eaten pretty much anywhere