Soap bubbles are always a perfect sphere unless you help them take on a different shape.
Soap bubbles that are not spherical are unusual and they don’t happen without a little help. Nature is funny like that. Square bubbles are easy to make and can serve as a great learning tool to explore solutions, soap films, and surface tension. You build a bubble maker that’s a cube, dip it into some soap solution, and the film stretches out flat. The film clings to the edges of the cube causing the bubble to appear to be a square. Well, it’s almost a square.