Towards the end of the movie, when all three are crawling through the Lincoln Tunnel, they are almost waist deep in water. Yet, the Secret Service lady's jeans change from dry to wet and back again. The same when she is chased back through the tunnel, her and the Secret Service guy's trousers are dry.
Shortly after the midpoint of the film, when Regis and Spikings sit down for a drink in the living room. We see an extreme close-up of Spikings saying "loneliest job in the world" as he takes a sip. There is a tiny grinning skull / demon face in the ice in his glass.