[OJFord]

Exactly my thought - I scored 5/6 choosing very quickly the one which seemed more imperfect at a glance, but I'm no Reddit-expert photoshop-identifier or whatever. They all looked real, I'd have assumed any of them were without the 'one of these is fake' context.

[KineticLensman]

I got 5/5 correct just by looking for weird artefacts in the hair and background. Just looking at the eyes alone was much harder (I sometimes couldn't tell).

[happymellon]

Ears and neckline are also good indicators.

Face on, ears seem to become smudges.