"Don't you try humor on them - really don't try - just "yes" / "no" and no smile - , or they'll really bite you !
One guy making humor almost got jailed - Listen carefully to their questions - you might be surprised by some ... Just stick to "yes" and "no" . "
this reminded me of my sister's story... with my, nowadays, 8 foot tall apple tree, she had put it in her luggage (14" including the root grafting). While passing through the customs in US they asked her if she had anything that's fresh , veggies, fruit and plants... She replies, "yes, I have an Apple tree in my suitcase" they all lough at her comment and let her go through... she was confused when she told me the story... But I didn't complain.
So, being honest , sometimes works the best.