If you think we've exhausted all secrets GTA 5 has to offer, think again.

Black Cellphones is the latest GTA 5 secret/Easter egg that sent the community looking for answers. Twitter user @KarmaIngram1 discovered that bringing up the in-game cellphone and dialling (1-999-367-3767) triggers an explosion in the sky, and changes the phone theme to black.

You can only trigger this in single-player, and changing character doesn't affect it. Interestingly, the game doesn't consider this a cheat code.

It's not yet clear what's exploded or what effect, if any, it would have on the game. Some Reddit users are thinking that the last two sets could be read as "EMP" or "EMPEROR" and so they're looking for references to these words in the game's files.

Watch what it does in the video below, courtesy of Yan2295.