This is a great question. In fact, the answer is no, not all bubbles are round.

Typically, bubbles are round except when they are moving. The short explanation for this is that when bubbles move through a fluid, such as air bubbles moving through water or carbon dioxide bubbles through soda, they are pushed on by the substance they are moving through in a way that deforms the bubble and causes it to lose its round shape. The substance the bubble moves through pushes on it unequally, with greater force pushing on the leading edge of the bubble in the direction it is moving and less force pushing on the trailing edge of the bubble. As a result, the leading edge of the bubble tends to flatten a little, causing the bubble to look more like a bowl than a round ball.

All bubbles are round if they are small and simply floating in the air not touching anything. The air inside the bubble pushes out the same in all directions and makes a round bubble. However, you can make bubbles of different shapes by touching them with soapy objects (dry objects will just cause the bubble to break). Try blowing a bubble and letting it land on a soapy plate - one side will become flatter. You can also push a soapy pencil through a bubble without breaking it. You can make tube-shaped bubbles by lifting a hoop from a tray of soapy water. Have fun playing with bubbles! Cheers.

A sphere is the smallest volume to surface area possible, so all bubbles will be drawn to a spherical shape in the absence of other forces.

Unsupported bubbles (if they are not lying on some surface) are always spherical because the soap film pulls in the bubble and the sphere (like a ball) is the best shape for this.