I picked this up over at nofilmschool.com.
We’ve seen these kind of tweaks in the forum (like here) several times before, but never explained in the form of a nice and poppy music video like this one.
The idea is to cut out your desired shape of bokeh from a piece of black paper and hold it in front of your lens and voilá there you have your custom shaped bokeh.
The people behind this short clip are both called Daniel thus calling themselves DANIELS.
“Koo” who writes the nofilmschool.com blog recently also presented DANIELS’ new music video by the band “Manchester Orchestra”. Apparently shot on dslr and definitely worth checking out: