555 in North American films and television shows

[ROBINDESBOIS]

Why do phone numbers of American films and tv shows start with 555?

[Rusty]

This used to be a 'safe' prefix to use, because it wouldn't actually dial anybody. Except for a few numbers, like 555-1212 (directory assistance), the prefix used to be reserved. However, since 1994 that is no longer the case (a few are still reserved in that prefix that can be used for fictitious numbers).

[ROBINDESBOIS]

Do you mean that the prefix is not in use anymore? Only for fiction numbers?

[Rusty]

No, I said it is in use, since 1994. It didn't used to be in use, except for a few numbers reserved by the telephone company. That's no longer true.
They still try to use fictional numbers in movies, but some of them actually belong to someone now.

[Caballero]

Very few belong to anyone. Although I heard that some are nationwide (e.g. they will call the same number from any area code.)

If you need a fictitious phone number, you can use

555-01xx where xx is from 00 to 99
they are reserved, according to Wikipedia.

But what is even better is to use the area codes 958 or 959, because Wikipedia says they are reserved area codes. And they look like real cities, but they're really not.