this guy told me recently that in Israel, where he lives, his friends saw his wife out with another man. they staged this intervention type thing where they broke the terrible news that his wife was cheating on him. He then had to explain to them that they have a poly relationship and it's fine. They eventually accepted this, or so he thought, until his best friend phoned him in tears saying that he knows he made that up on the spot to save face and that he is here when he is ready to talk.
Another funny thing I have heard was that a guy was chilling with a regular date at his house, she was browsing his fridge and came across some leftover Shepherds pie which she asked if she could eat. Now the guy, being a guy perhaps, didn't think about this before telling her to go ahead. After, she commented on how delicious it was and asked if he had cooked it, to which he replied that no, his other partner had (obviously the poly part was all in the open from the get go) and she totally freaked out and acted as if she had been poisoned.