3. Avengers: Infinity War
The posters for Avengers: Infinity War are packed to say the least, and its IMAX one-sheet is no exception. Displaying most of the film's characters in grand heroic poses, it doesn't seem like there's much room for anything else of note, but those cheeky folks over at IMAX managed to slip in a few easter eggs anyway.
Naturally - and as was the case with every piece of Infinity War marketing - fans scoured this thing for days looking for secret details, and eventually, someone over on Reddit stumbled upon four hidden IMAX logos dotted across the top-half of the poster.
Each logo - or rather, each "IMAX" word - is drawn in a scrawly, hand-written font, so blends seamlessly into the background of the image.
How did fans uncover this? God knows. Stuff like this really makes you wonder if some people have too much free time on their hands...