What was the most anachronistic thing you've seen in a fictional work that wasn't intentional or an accident?

[terentii]

@phs3

For me, it’s always lighting and their attitudes toward it: a room long pre-electricity with one person in it will have several lamps burning, and they’ll go outside without putting any of them out (or taking one with).

The room is always way too brightly lit for just candles or oil lamps. The only movies I can think of that portrayed this realistically are Barry Lyndon and Heaven’s Gate.