Unknown form of known object
Some things (in this case - pineapple) may be presented in different shape than one we expect of them to be. For example, rather rectangular pineapples may seem wierd for someone. But being not like others doesn't always mean being worse.
And more than that there can be some advantages. Usually pineapples mean pineapples and do not mean anything but fruit of this kind.
But in case they are rather rectangular 3d shapes they suddenly mean something else like exotic hotel building or unusal package boxes. And the list can be continued on and on.