it's kosher for passover!

so i'm eating some tasty sushi for fish friday along with some creme cheese that tells me that it is "kosher for passover". so what makes me wonder is, is it ever NOT kosher? it's cheese! what could they be doing to it, for it to not be kosher? making it from camel milk? slicing in with a bloodied blade they just used to slaughter a cow? not that i ever keep kosher, i'm shiksa all the way, i'm just curious about what my cream cheese would have to do to be unfit? if you know tell me, because i'm very curious.