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.

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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?