Movies have been using 555 numbers for a long time. According to Telecom Heritage, Hollywood was probably first encouraged to adopt this practice in the mid-20th century because, at the time, the 555 code was dedicated to services such as repairs, operators, and so on: this meant that there weren't many real people who had 555 numbers. Why does this matter? Well, imagine that a blockbuster film depicted a villainous corporation selling toxic slime energy drinks, and the corporation's phone number was your number. Would you really want to receive hundreds of calls a day, asking for toxic slime energy drinks? Probably not.

Hence, movies use 555 numbers, and books and TV shows soon followed suit. While it's not entirely clear which movie was the first one to embrace the 555, Academic writes that one of the earliest was the 1962 film Panic in Year Zero!, which used the number 555-2106. Another factor that may have encouraged the use of 555, according to Mental Floss, is how memorable it is. The repeated digit probably helped it gain traction, helping it to become widespread across the media landscape ... and, yes, eventually resulting in articles like this one. 

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