Spot the difference Memes

When mathematicians play "spot the difference" games! On the left, we have the integer 4, while on the right we have the set notation for 4 in von Neumann ordinals where each number is represented as the set of all smaller ordinals. Mathematical equality doesn't care about your superficial differences—they're fundamentally identical despite looking completely different. Only a mathematician would create a puzzle where the answer is simultaneously "they're completely different" and "they're exactly the same thing."