The phrase "little pineapple" is used metaphorically to describe something or someone small in size. It means that the thing being referred to is small, just like a small pineapple.
Sentences with «little pineapple»
I love the unique style and the fun little pineapple purse you've paired it with. (dailykongfidence.com)
On another note, I feel fortunate to have two little pineapples growing outside in our backyard garden right now: — RRB - Don't know when to pick them, though! (101cookbooks.com)