At some point in most people's social lives, a film comes up in conversation that they have not seen but said they had. Not a complicated lie - just a small affirmative nod, a vague "yes, I saw that," deployed at a moment when saying otherwise would require more explanation than the conversation could bear.
The question of whether this is actually wrong is more interesting than it looks. The harm is not immediately obvious. No one is deceived about anything important. No decision is made on the basis of false information. The conversation continues. Everyone goes home.
And yet there is something slightly uncomfortable about it, and that discomfort is worth examining. The lie is, on inspection, not really about the film at all. It is about social belonging - the desire to be someone who has seen the right things, read the right books, knows the references. The film is just the occasion. The deeper thing being faked is cultural membership.
What makes this category of lie interesting is that it tends to be self-defeating. If the conversation continues, you will eventually be asked something specific. Which scene. Which actor. What you thought of the ending. At that point the lie either collapses or requires another, slightly more elaborate lie on top of it. The cognitive overhead climbs rapidly.
There is also the question of what the original lie was protecting. If it was protecting the other person's feelings - you did not want them to feel their recommendation had gone unheeded - that is at least an honourable motive. If it was protecting your own image - you did not want to seem like someone who had not seen it - that is a slightly less flattering motive but an entirely human one.
The most honest answer is probably that it depends on the relationship and the moment. In a casual conversation with an acquaintance, it is approximately as wrong as not correcting someone who mispronounces your name because it would be awkward. In a close friendship, it is slightly worse, because close friendships work on the understanding that you can say "no, I haven't got around to it yet" without the sky falling in.
You almost certainly already know which kind of lie yours was.
Disagree? Say so.
Genuine pushback is welcome. Personal abuse is not.

