I get the concept of introducing tiny errors to make it look better, but I disagree with almost all of the examples you cited. For the bird one, the shape of t

I get the concept of introducing tiny errors to make it look better, but I disagree with almost all of the examples you cited. For the bird one, the shape of the bird in that cage is different than the other yellow birds, but is identical to the black one. So that bird was probably originally black, then was edited to be yellow but they forgot to restore the black bars over it. For the moon one, that's extremely implausible. It's a tiny rope, right next to a large shape that clearly cuts across the moon. Having it go behind the moon doesn't make the moon stand out any more, it's simply an error. In addition, the moon isn't even the focal point of that image, it's a fairly incidental detail (hell, it's almost hidden behind the house). The toe one is the only one that I think is plausibly intentional. For the tree one, I agree that the scene was likely drawn without a sun, then the sun added in after. But that does make it an error, because they decided to stick a sun somewhere that clearly contradicts the lighting on the rest of the stamp.