What's a detail in a film you noticed that nobody believed until they rewound it?

I'm building FrameHunt — a film and TV tracker where you can also post the hidden details you spot: Easter eggs, background props, license plates, continuity slips. Each one gets a timestamp so other people can go check the frame themselves.

Before I launch here on Sep 29, I want to collect the good ones.

Mine: in Fight Club, Tyler Durden appears for a single frame in four scenes before he's introduced. I spent a whole evening pausing to find them and my flatmate refused to believe me until I showed him.

What's yours? Film or series, and roughly where in the runtime.