If you're served lobster at a dinner party, you shouldn't start talking to it. But that's what happens in this film, in which corporate investment executive Tim (Paul Rudd) is challenged by his boss to invite a moron – or "schmuck" – to a dinner party in order to compete for a promotion: whoever brings the biggest schmuck wins.

Tim brings Barry (Steve Carrell), a taxman and mouse taxidermist; among the other schmucks at the dinner are a mind controller, a man with the world's best beard, and a woman who talks to dead pets. She starts channelling the lobster's thoughts as it's placed in a vat of boiling water, which rather puts everyone off their food. Talking to one's dinner really isn't the done thing – but then neither is it advisable to invite people in order to deliberately humiliate them. That goes against the two basic rules of good etiquette: to respect people, and to put them at their ease.

I've never sat next to anyone at a dinner who stuffed dead mice for a hobby, but one does occasionally find oneself sitting next to slightly peculiar people. If that does happen, the last thing you should do is openly laugh at them. I actually prefer meeting quirky people – they're often far more interesting than bankers.

The dinner soon descends into a huge fight. That's never happened at a party I've been to – though if it did, I wouldn't just stand back, as the guests do here. I'd wade in and split the fighters up.

Tim eventually realises that he is the real "schmuck", not Barry. Though I don't stuff mice myself, I felt a certain affinity for Barry. I've also stood outside the norm. I don't go to nightclubs, I don't drink, and I started becoming interested in manners when I was still at school. A lot of people said, "Oh God, he's lost it – there's this 17-year-old teaching etiquette." And now here I am, reviewing a film for the Guardian. Like Barry, I've come out on top in the end.

William Hanson is a freelance etiquette consultant; see williamhanson.co.uk. Dinner for Schmucks is on general release