There’s some thing called a LEGO lenticular, which I never heard of until today (regretfully). Basic idea is that the artwork gives two different images depending on the angle from which you look. This specific one happens to be Batman from one side, and his arc-nemesis, Joker, from the other. Think back to those hologram cover from the 90s, but cooler. This work was done by Arthur Gugick, and you can get your mind blow with the video below.