The easter egg that has been found is Overwatch newest character, Hammond ‘The Wrecking Ball’ singing along to the Overwatch theme tune. Hammond will only start singing if you play a tune first. For this, you will need your weapon and some bells which are located on the Dorado Map.
To learn more about the latest addition to Overwatch, check out this guide – Hammond ‘The Wrecking Ball’ Hamster Guide (Overwatch)
How to Get Hammond to Sing?
You will need to hit the Dorado Bells that overlooks the courtyard on the Dorado Map in a sequence. At the end of the game, there is a little segment you hear, this is the segment that you will need to play using the bells.
You ring the bells by firing your weapon at it and the trick is to fire at the bells in the correct order. The starting point of the sequence is the top middle bell and once you have hit the last bell in the sequence, Hammond will sing his heart out to you.
Full Sequence: Top middle, Top Left, Top Middle, Top Right, Top Left, Top Right and the last on to your right on ground level.