It's the unspoken rule of 4chan Which goes like this. If OP demands something (Most likely a specific number at the end of a post) And some random lucky anon Happens to get it, OP is Obligated to do the deed he promised to do. Most OP's don't follow their demand tho, but these are the lucky ones that did, and we got a really good laugh out of it. Almost too funny to be true, and that's the best part of 4chan. Almost makes me want to return, but nowadays /b/ (aka the place where all the funny shit happens) is mostly full of Pr0n threads and other threads mostly affiliated with sex, or sexy women Which is sad since /b/ used to be a fun place. Here's another random thread i found really funny