Check out the artist's killer look from Tuesday night's festivities -- the dude's a spitting image of the big screen Batman, and on top of his picture-perfect costume, he was riding around Hollywood in Batman's Tumbler ... the Batmobile of choice in the Christopher Nolan movies.

Diddy rented the iconic ride from TV Show Cars out of New Jersey and had it transported across the United States.

As we reported, Diddy told Jimmy Kimmel he was going to step up his Halloween game this year -- after saying last year's insanely good Joker costume resulted in WB claiming it was a copyright violation.

Kimmel told him to just dress up as Heath Ledger's character again, despite the heat, but Diddy warned his costume this year would also have WB lawyers working overtime ... and he was true to his word.

And then there's the actor's union -- SAG said it didn't want its members dressing up as movie characters for Halloween, but Diddy, and several others, are clearly ignoring that demand.

Batman was tripped up by one Halloween goblin ... fuel mileage. His Batmobile ran outta gas on Sunset Blvd!!! Of course, he's got people for that, and one of 'em fetched a gas canister for a refill -- not the hero Diddy deserved, but the one he needed!