Pet tikvica, molim vas means “Five courgettes, please” – and it demonstrates a peculiarity of Croatian: from the number five onwards, the ending of the following word changes. Tikvice becomes tikvica.
That is why the sentence gets its own image: you claim you can fit five courgettes into a plastic bottle – the bottle being the five from the navel. A touch of courgette sticks out at the top, everybody makes jokes, and you bite a piece off with your tooth so it fits. The tooth at the end is the changed ending.
This rule applies to every quantity from here on, which makes this one example particularly worthwhile.