Katy Perry, Orlando Bloom We Party Like Bill and Hillary!!!

Katy Perry and Orlando Bloom shamed all the celebrity guests at Kate Hudson's Halloween party ... not only dressing up exactly like Bill and Hill, but showing up with a phalinx of Secret Service.

The video's hilarious. Although the party was held behind gates, they opened for the big Presidential reveal, with a wonky Trump flanking the couple.

The getups were incredibly detailed ... it took Katy a long, long time to nail down the look.