Paris Hilton -- Heads and Shoulders

10/22/2010 6:20 AM PDT BY TMZ STAFF
When it comes to Halloween shopping, Paris Hilton believes three heads are better than one.

Hilton and her BF Cy Waits ... and two of her dogs ... hit a West Hollywood costume shop yesterday ... and (surprise!) tried on a bunch of really provocative outfits!

Trick or treat?