What to Wear: Lo and behold, another look where the mask is very important. You might be able to make it yourself, if you can find a basic clown-faced mask. Just add a brain and ruffle collar and you're good to go! The rest the outfit looks like a lot of navy. A long-sleeved shirt or sweater, a vest, pants, fingerless gloves. You get the picture.
How to Act: This is the other half of that awful clown sex scene in the grocery store, so maybe that should be your jumping off point. I don't know . . . couples costume?