So this is something I would probably have done months ago if I had money to spare on pineapples. Sadly I don't so, having been reminded today, I thought I'd post it here.
So the thinking is as follows: a) Pineapples are funny looking fruit. They're kinda spiky and have those amusing big green bits sprouting out of the top. And even though they can be easily bought at most supermarkets they aren't considered common fruit in this country; not having been programmed into our consciousnesses from childhood with that whole A for Apple, B for Banana thing.
b) There are certain places people don't expect to see fruit.
I was reminded of this idea today because I saw a banana lying on the ground by a building. Obviously a banana had been dropped and that was that. But what if there were a pineapple sitting on a postbox/street-light/bus shelter; that's extremely random, not readily explainable and will make people stop and look. Obviously this can be achieved in various public places with a variety of fruit, the more comical the better.
Speaking personally if I were walking through a public place and saw a pineapple (or something like that) innocently/stoically sitting somewhere unusual it would put a smile on my face.