The effect you are seeing is called Bokeh. It is how a lens renders out of focus highlights. While glass aberrations and coatings play a part, the blurred highlights tend to take on the shape of the aperture. They are, after all, basically the inverse of a shadow cast by the aperture into the film or sensor.
Since the effect is heightened by shallow depth of field and since depth of field gets shallower with wider apertures, bokeh tends toward circular shapes. However, a small reduction of a modern bladed aperture will reveal a more polygonal structure. Shooting wide open and using a faster shutter speed will give the circular shape.
The size of the highlights is a combination of the size of the light source from which they originate and the brightness of that light source. A fine mist with reflected flash is capable of producing both large and small bokeh. They key is how distant the drops from the center of focus, not the distance of the drop from the lens.
You should be able to get this effect with any lens, although with today's lenses the effect is more dependent on the aperture then lens aberration because the quality of the glass and the coatings has improved over the years.
This is a bit outside the scope of your question but since the bokeh tends to take on the shape of the aperture, it is possible to use cut-outs in front of the lens while shooting wide open to manufacture specific shapes for your bokeh. I once cut a cross shape into a filter mask to obtain cross-shaped bokeh and it worked quite well. In the image below, I tried to get the feel of lotus flowers by using a filter mask into which I'd cut the main shape but left a small spot in the center. Note that the bokeh on the figure's cap also reflect the same shape, but are quite small due to their proximity to the field of focus.