depends what u mean to buy them you go to madam malkins right behind the weasly joke shop to buy them go to a unlocked character and press "a" on the wii xbox 360 or ds (idk about the psp or ps3) to play as them you can use free play on missions or use the polyjuice potion outside of them you unlock the polyjuice potion after "the seven harrys" on the wii (i think, maybe later)on the ds it is automatically
unlocked (not sure about xbox or psp this time) hope this helps.
« Last edited by on Feb 11th 2013 »