Yes, apparently that´s a thing, hidden achievements! Not even showing in your log as incomplete. I discovered this today, thanks to Mmrrggll (a youtuber I just started following)
For this one, all you have to do is get together with 4 other people and jump at the center room at Thunder Totem.
It´s called Drum Circle
We tried to match our jump, but as it turns out, it´s not easy to organize :p But in the end, we got credit for it, while 2 of us were standing still!
Let this be the out of the ordinary thing you do today! 🙂
Did you ever notice that drum sound when jumping around by the way? I sure didn´t.