Bicycle cards are made up of three layers of card; the two faces and a centre piece.
There are others on the forum who have had experience with the type of ink used on the cards, so they'll give you more detail, but basically the ink is as permanent as it can be. if you try to take the ink off you'll also be taking a layer of card off aswell.
It sounds like your cards are just misprinted, which is a shame. Not a huge deal though, so don't worry about mistreating them. Keep them in a cage under the stairs if you want, and only feed them mouldy bread and stagnant water.
