I don’t know how to comment when I see this. I want to talk about how this works, but most people know how this works. So I don’t know why its a thing. Its funny though.
This particular version is more about the characters depicted (Denji and Power from Chainsaw Man), who are famous for being endearingly stupid.
The more earnest versions you tend to see on TikTok are mostly posted by, or at least targeted at, actual kids who don't yet understand how vision works. Nobody on Lemmy is under the age of 30.
I would like to hear an actual explanation. I don’t know shit about light physics but my attempt to explain it is that the trajectory of the light is such that it reflects off of the egg into your eyes and that it is this trajectory that is reflected in the mirror.
My wife was having a brain fart once and knew there was a logical reason but couldn't figure it out atm. So I drew a diagram top down geometry class style. Set her straight just like that. It's just the light bouncing at an angle so that you can see what is on the front of the paper.