The duck can be used for both tricking reviewers as suggest, but also for making sure the thing you asked to be reviewed actually got reviewed (if they don't find the duck, did they really review it?).
In the contract for a Van Halen concert, there was a line telling organizers that there should be a bowl of M&Ms, with all the brown candies removed. Otherwise the show would be cancelled at full price.
Even though it sounds just like another eccentricity from celebrities, the idea was that if brown M&Ms are present, it meant that organizers didn't read the papers, which also contained safety-critical points.
I put a picture of “this is Sparta” in my portfolio. So far, no company has asked me about it. But if they did, they’d get extra preference from me, since they actually looked at my work.
I remember seeing that in a portfolio when I was reviewing candidates and thought you might not be serious about the job or that you made a mistake, which highlighted you as a risk. As such you did not make our preferred candidate list.
The legend is that this explains the scene in Buckaroo Banzai that includes a watermelon in a hydraulic press. It was added to see if anyone at the studio was paying attention, nobody noticed it, and they left it in anyway.
