The movie is set in 1995, yet Chuck's Jeep Cherokee is clearly at least a 1999 model. The newly styled front end first appeared in 1997 models, and the wheels were first available in 1999. The dashboard and instrument cluster are from the newer model. The front blinkers on the 1995 Cherokee were attached to the headlights, not on the front fender.
The taxi that carries Chuck back to Kelly's home has its "For Hire" light illuminated. Usually on a taxi with a fare onboard, this light would not be lit, but the driver simply forgot to turn it off (which happens regularly in the real world).
In Kelly's kitchen, she explains to Chuck that the Titans made the Super Bowl and "almost won" but for one yard. In fact, had the Titans scored, the score would have been 23-22 and the likely result would have been an extra point kick that would have tied the game.
When Chuck throws the boxed volleyball with his bloodied hand after the failed attempt to create fire, the box is right-side-up; since he bends down to pick it up, this means that the fingertips should be pointing down on the ball. However, when he looks at the ball soon after, the box is upright but the fingertips are pointing upwards.
Right after Chuck cuts his hand, while he is trying to create fire, the boxed volleyball is sitting on the ground with the black part of the box on the right hand side. When Chuck goes to pick it up to throw it, the black part of the box is now seen on the left hand side.
When Chuck is boarding the airplane after kissing Kelly goodbye, the aircraft's tail fin has no engine mounted to it. This proves that the airplane used in this shot was not an MD-11, which was used as the model for the cockpit scenes later in the movie. MD11s have an engine mounted on the tail fin, three thrust levers between the pilots, and 6 digital cockpit screens.
In the scene where Chuck first finds the port-a-potty piece that washes up on shore, the first shot revealing his left thigh does not bear the long scar shown earlier in the movie. Yet in the scenes afterwards, the scar appears once again on his left thigh.
When Chuck is first trying to make fire the volley ball in the background has a logo visible in the left top corner of the box, but after he cuts his hand, the next scene shows the volley ball box in a slightly different position and without the logo.
When Chuck stabs a crab with his spear, there are eight thin legs all the same width wiggling. Then as the crab drops off camera and Chuck breaks off a leg, the claw that comes back in shot is much bigger.
When Chuck enters the cockpit, the altimeter selection of the Primary Flight Display should be completely brown because the plane is in a steep drive. It shows a pitch indication of zero, or level flight.
As the FedEx MD-11 dives toward the ocean, none of the alarms that should go off during a steep dive (i.e. Excessive Sink Rate, GPWS) are going off. All aircraft operating out of the United States since 1972 have been equipped with such alarm systems to help prevent crashes.
The plane that Chuck was on took off from Memphis, and crashed somewhere in the South Pacific. But at the end of the movie, he delivered the FedEx package he didn't open on the island to an address in Texas. While it seems odd that a package bound for Texas would be on an international flight from Memphis, the woman who lived there was actually the sender of the package and Chuck was returning it to her (hence the soundtrack playing Elvis Presley's "Return to Sender" when he's driving there). The same woman had sent a package at the beginning of the movie to her husband in St. Petersburg, Russia, with similar golden wings painted on it.
When Chuck carves HELP in the sand with his foot, you can see the high tide mark of the sea weed is below the letters and the sand is obviously soft indicating it is above the high tide mark. However, in the next scene when the tide has come in and washed half the letters away the high tide sea weed mark is up above the letters.
When Chuck compares his foot to Albert's shoe his toes hang over the top of the shoe. When Chuck puts the shoe on with the toes cut out, the shoe actually fits his foot. The toes being cut out was just a visual effect.
Early on in his ordeal and early in the morning when Chuck sights a light off on the horizon, as he is prepping to paddle out to the ship which he assumes is there, you can see the rising sun in the same direction off to the left of the light. However, as he starts his short ill fated journey towards that ship's light, the sun is behind him.
The goof item below may give away important plot points.
When Chuck buries Albert Miller, he scratches "1950-1995" on the rock face above the grave. When Chuck examines Miller's wallet, you can see a close-up of Miller's New South Wales, Australia, driver's license, with a birth date in 1949.