If there's something strange in your neighborhood, who you gonna call? As we all know from Ray Parker, Jr.'s theme song, the answer is the Ghostbusters. In the 1984 movie, we even see a phone number for the fictional paranormal exterminators. The Ghostbusters hotline pops up on a television screen during the rise-to-fame montage in the middle of the film. "Our courteous and efficient staff is on-call 24 hours a day to serve all your supernatural elimination needs," Ray (Dan Aykroyd) explains. You only have to dial 555-2368.

Some astute TV lovers in the audience probably recognized the number. From 1974 to 1980, that was Jim Rockford's phone number. In the opening credits of The Rockford Files, the camera pans across the cluttered desk of the unconventional detective. We hear his phone ring and his messages play. The camera pushed into the black telephone and we see the number: 311-555-2368.

But Rockford was not the only one to use those 10 digits. Not by a long shot. Oh, if you wanted to reach the Bionic Woman? You could reach Jaime Sommers in her coach house residence at — you guessed it — 311-555-2368.

A few years earlier, the same phone number turns up on The Mod Squad, in the 1971 episode "…And the Children Shall Bleed Them." In the Mannix episode "Memory: Zero," our hero uses a pay phone with the same number, as seen in the upper left up top.

Even before the era of seven-digit phone numbers, in the age of telephone exchange names like PEnnsylvania and BUtterfield, the same number turns up on television.

"Night Call," a fifth season episode of The Twilight Zone from 1964, centers around an elderly woman who keeps receiving disturbing phone calls. Take a good look at her phone. You can also see it in the image above. The number printed on the dial is KLondike 5-2368, or KL 5-2368. Of course, to dial "KL" you press "55."

So the big question you're probably asking is, "Why?" This convenient fake number did not originate in Hollywood, rather within the phone industry itself. For years, industry giants like Bell Systems and Western Electric were using KL 5-2368 and 555-2368 as dummy numbers. If you saw a telephone for sale at some point in the midcentury, it likely had the same number printed on it. It often popped up in advertising, too. At the top of the page is a Western Electric print ad from LIFE Magazine in 1961. You can also see it below on the right, on a 1962 Pacific Telephone brochure promoting the switch-over from manual switching to direct dialing.

Image: classicrotaryphones.com

As for the 2368? That stood for CENT, as in CENTral. Going further back, you can find Bell using EXchange CENTral in its advertisements.

During the shift to seven-digit numbers in the 1960s, telephone companies encouraged TV producers and filmmakers to begin using the 555 exchange.

There have been others besides 2368. Homer Simpson promotes his Mr. Plow service with the number KL5-3226 in a classic episode of The Simpsons. Screech sold spaghetti sauce over the television on Saved by the Bell via 555-MMMM. Kramer's number on Seinfeld was 555-FILK, just one number away from Moviefone, 555-FILM.

As for reaching Rockford today? Don't try it. That '311' now gets you to non-emergency services.