If you don't own a costume and were invited to a Halloween party, you should try the Pop Art look:
First, use a black eye-liner to fill in your eyebrows and line your facial expressions.
Then, outline your lips and apply eye-shadow on your lids.
Outline the eyeshadow on your lids, and use two different lip color tones to paint your lips. Use the darkest lip color as your lip base, and the lightest one to create the glossy cartoon look.
Paint red dots, uniformly, all over your face, and finish the look by applying mascara and/or falsies.
The final look
My friend, Breana, tried to achieve the Roy Lichtenstein's blonde girl look, but you can search for other characters and do the same. I think this is a very rare Halloween costume, and a great idea if you really want to stand out from the crowd. I was thinking about trying it out myself and painting some vampire fangs on my lips, but I guess it'll have to be next Halloween, since I already have my costumes.
I hope you try this costume idea, for which you only need make-up and a cute dress.