Yes, you may have already purchased the four-pack of Krog & Friends pins, but that set lacks the wily visage of Merg!  And how can you call yourself a real collector if you don't have... ALL of the Krog & Friends pins?!

Seems like the kind of scheme Merg would've thought up, to be honest...

These are official Pinny Arcade pins and thus can be traded for other Pinny Arcade pins, if that's something that interests you. You can look here for the general rules.