During the costume party when Pete and Melissa are slow dancing, a black patch appears and disappears from Pete's racing outfit between shots. He never had it on before or after the dance with Melissa.
Just after the bullfight, Aunt Louise knocks the shoulder ornament off Captain Blythe's uniform as they get out of the car. By the time we see Captain Blythe outside the car, the ornament is back in place.
Though the ship scenes are supposedly set on the Sun Princess, at least three different ships' exteriors are shown during the course of the movie. Herbie is shown being loaded on to the actual Sun Princess in the beginning, but later, aerial shots of the ship are actually of the Island or Pacific Princess (aka The Love Boat), which, whilst still a Princess ship, has a differently-shaped funnel. When Herbie is dispatched into the drink, the scene is set on an entirely different ship all together; you can see two orange funnels in the background, when in fact the Sun Princess has only one aft funnel with Princess' trademark Seawitch on it.
When the bus finally breaks down, first it is shown with the radiator cap off blowing steam under pressure out the top of the radiator. Then you see a close-up of the radiator top with the cap still on, but loosely, and the cap comes off and steam begins pouring out.
After Shepard pushes Pacho onto the ground in the jungle, Quinn says "I don't like leaving that kid back there" and Shepard says "Don't worry about him! He's not going anywhere". If you're watching with closed captioning turned on, Shepard's name is displayed on the caption as Quinn speaks and then Quinn's name is displayed on the caption as Shepard speaks.
Captain Blythe says he is wearing a replica of the uniform Lord Nelson wore when he defeated the Spanish Armada. Although the Battle of Trafalgar Bay (1805) is chiefly remembered as a battle between the British and the French, the Spanish fleet was also involved. The combined French-Spanish fleet took a severe beating from the British Navy (which had very few casualties, though Nelson himself was mortally wounded by a French sniper), so technically Nelson did defeat a Spanish Armada.