Battlefield 1/April Fools' Day
On April 1, 2017 an update added a meteor to the map Suez, with a tiny button on it that triggered morse code when interacted with. The morse code translated to BZIIRNIULIZUXIXHYHIUOAIPENOMAKTLMYUGRPKUMTZHIIDWTLTMTF.
On the outside of the meteor a fence with cables could be seen, while on the inside there was a well, a gramophone speaker and five wooden boxes. The objects found inside the rock could only be seen by glitching through certain parts of the meteor, though due to the easiness this could happen it was suspected to be intentional.
The ciphertext was finally deciphered on July 20, 2017. The encryption method was the same as the one used for the ciphertext on Soissons, part of the A Conflict phase of the multi-phase easter egg.
Upper-right Square Key: MASTERZYXWVUQPONLKIHGFDCB
Lower-left Square Key: MANZYXWVUTSRQPOLKIHGFEDCB
Plaintext: YES THAT IS RIGHT IT IS TIME TO CELEBRATE APRIL THE FIRST WHAT A DAY
Additionally, unicorns were temporarily added in the game, replacing the horses when using the White Gray skin for cavalry. The unicorns could talk, as well as emit a rainbow from their horn. Performing five consecutive jumps in one run generated an even bigger rainbow, emitted from the unicorn's tail.