In University of California undergraduate computer science courses (probably other, similar places, but this is where I encountered it) the Gilligan's Island rule provides an amusing way of defining a rather draconian non-interaction policy. To wit: any discussions regarding assigned code must take place without the aid of laptops or other note-taking devices; after such a discussion, all involved must perform a non-code-related action for at least half an hour. This is to minimize similarities between the code of different individuals in a single class, essential because comparison between code (to check for cheating) is often done through automated methods.

Watching something inane like Gilligan's Island on television satisfies this rule, hence the name.