How could msg.sender != tx.origin AND extcodesize(caller) == 0 be true?

I'm working on a puzzle where msg.sender != tx.origin, so the implication is that the caller needs to be a contract or at least something in between the calling account. But extcodesize(caller) == 0 also needs to be true. So the caller needs to be an address or externally owned account. How can both of these be true? Can the caller's codesize ever be 0 if not an address/EOA?