The performer displays a plain cloth bag with spots printed onto it.  Also displayed are two handkerchiefs, one black & one white, now the fun starts...  The bag is shown inside out to show it's black on the inside and there's nothing hidden, the scarves are placed into the bag with the claim that they're going to change colour.  Indeed they do, the white one is now black, the black is now white.  Your audience are not convinced, so you now claim to repeat the trick, but this time they're going to be covered in spots.  The scarves go into the bag, a magic word is announced, both scarves are removed as the magician now points out that they're covered in spots.  The white one is covered in white spots, the black one is covered in black spots.  The audience are now fully unimpressed, not to worry, you are now going to transform them into spots of the opposite colour.  Once again they go into the bag and given a little magic influence.  This time they're covered in spots of the opposite colour, claiming to count the spots, it seems there's one missing...Where's the missing spot, turn the bag inside out and there it is...it's 'Spot The Dog' as the bag becomes a glove puppet with a cute dog face on it.