[charcircuit]

I'm not really sure this meme has a punchline. The number of instructions decreases in each panel.

[notriddle]

The punchline is that they use an instruction that Intel themselves do not recommend.

[jleahy]

The punchline is that they didn’t think of:

movzx rax, al

mov al, [rax+rbx]

[mizaru]

movzx eax, al

is one byte shorter, but I'm not sure if any of this would make a difference. x86 is tricky.