WARNING: The following contains SPOILERS for The Diplomat!During the closing credits of the Netflix series The Diplomat season 1, a British man's voice can be heard cryptically identifying as Dolphin 3-6 over radio communications. This hidden audio is embedded fairly deeply into the end credits with two minutes and 30 seconds left in season 1, episode 8, titled "The James Bond Clause." Many viewers might have missed this detail after the series finale of The Diplomat if they did not manually choose to watch through the end of the credits. The radio transmission comes after an explosive season 1 finale that leaves the future of several characters uncertain until season 2, which Netflix recently confirmed.
https://screenrant.com/the-diplomat-post-credits-dolphin-code-season-2-setup/