Goofs

When Robby first takes off his shorts on the beach, his body appears fairly evenly tanned, buttocks included. In the following scene, when he is splashing around naked in the water with Friday, he has a well defined tan line and his buttocks and groin are almost white in comparison to the rest of his tanned body.

Robby has two different pairs of cut-away shorts in the movie, one being a tighter fit,the other having a vertical tear on the leg.

Robby's red and white striped t-shirt changes back and forth from a tight fitting shirt to a much looser, obviously larger shirt that he tucks into his shorts.

Robby and Friday are both clearly circumcised. This makes sense for Robby, an American kid, but not for Friday, as circumcision has never been common practice among tropical island natives.

The native boy has supposedly been alone on the island for some time but his hair is very short and neatly trimmed.