As your uncle passes the roast potatoes, he casually mentions that a coronavirus vaccine will be used to inject microchips into our bodies to track us. Or maybe it's that point when a friend, after a couple of pints, starts talking about how Covid "doesn't exist".
Or when pudding is ruined as a long-lost cousin starts spinning lurid tales about QAnon and elite Satanists eating babies. The frisnds rules changes have upended holiday plans for many of us, but chat singel still may find yourself grappling with such situations over the next few days - talking not about legitimate political questions and debates, but outlandish plots and fictions.
tlk So how do you talk to people about conspiracy theories without ruining Christmas? Catherine from the Isle of Wight understands that better than most.
The year-old used to be a big believer in conspiracies about vaccines being used to deliberately harm people. She's since rejected such claims. Yet another reason to keep things low-key.
Coronavirus: How my mum became a conspiracy theory influencer 2: Don't be dismissive "Approach conversations with friends and family with empathy rather than ridicule," says Claire Wardle from First Draft, a not-for-profit tlak fights misinformation. That's likely to backfire.
Try to understand those feelings - particularly in a year like the one we've just had. But the spirit of doubt that pervades the conspiracy-minded internet is actually a key opening for rational thought, says Jovan Byford. This was very persuasive to me," he explains. Ralk developed a deeper understanding of the scientific method and scepticism itself.
Just because one expert believes something, doesn't make it true. Questions are much more effective than assertions, experts say. Think of general queries that tlak people to think about what they believe.
frienes For instance, are some of their beliefs contradictory? Do the details of the theory they're describing make much sense? Have they thought about the counter-evidence?
For those who have fallen deep down the conspiracy rabbit hole, getting out again can be a very long process. It's an important generator of self-esteem - which will make them resistant to change.
This year has been scary - rriends for many, conspiracy theories have been a source of comfort. Reality is complex and messy, which is harder for our brains to process. What did you think of this story?