Can there be a cubical bubble?
Although not physically perfect, a reasonable mathematical model for a bubble's shape is that it minimizes surface area subject to fixed volume.
A single floating bubble is usually a sphere, but bubbles only need to find local minima, not global minima. This makes more complicated bubble shapes possible.
In a YouTube video, a performer discusses making a cubical compartment inside a complicated bubble. Is this possible in a bubble with finitely-many compartments and no wires or other framework to provide additional boundary conditions?
Such a bubble is not actually cubical. See my answer on Quora.