It took me some time to get it. I’ll show these in the same order I saw them:
The first one might go unnoticed it you don’t look closely. The second one is really funny when you see it. And if you haven’t figured it out yet, the third one is the most obvious.
What an insight! The only thing I would have changed to make it a little bit more understandable is the position of the “favorite” slices. When you see 1 and 2, both have the “favorites” to the right, so there’s no much difference between one and the other, making it a little confusing to understand the joke. However, the third one works so well because the slices have different thickness over each person and the “favorite” is placed in the middle. Maybe the photo with the cat could’ve been flipped as to have it to the left side. That way the viewer would’ve been forced to look deeper to find the message.
Unless they did it on purpose!