First of all paint your nails black, I used Barry M - Black for this design
Next, using the brush in the nail varnish, paint a squoval shape on the corner of your nail, it's best to use an opaque colour for this if you're using a black background, I used Barry M - Blueberry
Next, using a small dotting tool make the ears and arms (Don't worry about it being completely even as the top coat will even it out later)
Then, using a thin paintbrush, or (if you wish) the dotting tool again, paint a thin black line for the mouth and add small white dots for the teeth using the same brush/tool.
Then finish off with a topcoat and you're done, you can also do this with other colours and body shapes as in the first picture using a similar technique.
I'm sorry it's a bit rushed towards the end, I didn't have much time, but I hope this was helpful!