Also, it’s similar for the hole. Where I think it came from is that the whole picture is slightly shorter in the first picture, and in the second, it’s slightly longer. The extra length comes together to form a hole. I used a ruler, and the second arrangement is around 1mm longer.

If you notice, the bottom edge of the first is slightly concave. Where the triangles meet in the middle are slightly higher than a straight line drawn between the bottom two corners.

If the second picutre, the bottom edge is slightly convex. The point where the triangles meet is slightly below a straight line drawn between the bottom two corners.

This slight change adds area to the overall rectanglur looking shape. But it doesn’t add more material, therefore there’s a hole.

INGENIOUS!

Now, to make the egg disappear: you can clearly see that on picture A, two eggs are incomplete. Egg #3 (we’re counting from the left here) is missing a tiny chunk on the lower cut of the card, and egg #6 (which happens to be number 3 from the right) is missing a tiny chunk on the upper cut of the card. These missing chunks are so tiny that you don’t notice it at a glance.

When the cards are rearranged, different upper parts of eggs are meeting different lower parts (hence making the eggs larger in size.) The missing upper chunk is meeting the missing lower chunk resulting in: VOILA, disappearing egg!

To make it simple, when you cut a picture of 8 eggs horizontally into two cards, you should have 16 halves of eggs. Eight upper halves and eight lower halves. Count the halves in this picture. There are only 14 halves, which, in turn, would make 7 whole eggs when you rearrange them.

Another thing I agree with Bob is: can’t figure out where the hole came from.