If the player uses their phone to dial 1-999-367-3767, it will connect the player to a caller known as Black Cellphones, which triggers an explosion right above the player's head. As the number is speculated to be numerical version of "1-999-EMP-DROP," the blast is rumored to be an Electromagnetic Pulse (EMP) and will set the phone's theme to the regular Gray and set the phone's background to a pure black which otherwise cannot be obtained. Dialing the number also causes the phone's model to grow by a small amount. In real life, an EMP interference is generally disruptive, or damaging to electronic equipment, and at higher energy levels, a powerful EMP event, such as a lightning strike, can damage physical objects, such as buildings and aircraft structures. In the game, it just causes a small explosion over player's head and change of player's phone color and size.
It is confirmed that the cheat code works with all the three game characters in single-player mode, but does not work online. Included with the code is the name of a mission called Ojasaud, meaning this number could be triggered during that mission. The problem with this is, that there is no such mission with that name, meaning the true meaning may never be uncovered. Some fans have theorized that it could be the name of a mission in a future DLC, and the Black Cellphones serve as an alternate reality game.
This may not be a paranormal occurrence, since 1-999-367-3767 also could translate as 1999-EMPEROR, which is the name of the color that phone's theme changes to.
Players also believe that this number could be a connection with a UFO, or even related to the Mount Chiliad Mystery. It also has been discovered that if the player goes on the top of Rebel radio tower and enters the number, morse code will play. It has not been decoded yet.
With the advent of GTA V for current-gen gaming platforms, namely Xbox One, PlayStation 4 and PC, Rockstar has introduced the ability to enter certain cheat codes as phone numbers using the player's in-game mobile handset. This could mean the number may be a leftover of a cheat code.