And then the real problem number 1. The answer is "Left - each figure contains an even number of arrow heads. Right - each figure contains an odd number of arrow heads"... but on the right I can clearly see that the three eggs across the top have an even number of arrowheads.
I won't share the solution (you have to keep some mystery in the world), but I showed this a year ago at a high-school reunion and five people independently found the same solution, so it should be well-posed.