devilish,
rascally,
roguish showing the cunning or ingenuity or wickedness typical of a devil; "devilish schemes"; "the cold calculation and diabolic art of some statesmen"; "the diabolical expression on his face"; "a mephistophelian glint in his eye"
elfish,
elvish,
elfin small and delicate; "she was an elfin creature--graceful and delicate"; "obsessed by things elfin and small"