You can try to create two (or many) nearby surfaces (with two different textures) which pass through one another..
You can also use a spot with an object that hides this spot and after lets pass the light to illuminate what you want.
I make a little example to show theses methods.
Lamp 1: a white sphere that changes size from 0 to 1
Lamp 2: two spheres, a black sphere of a fixed size 1 and a white sphere that changes size from 0.99 to 1.01
Lamp 3: 4 spheres, One is a black sphere of a fixed size 1 and 3 spheres of 3 different colors (red, green and blue) whose size varies from 0.99 to 1.01. There are also 3 cones (red, green and blue) whose size varies from 0 to 1.
Lamp 4: no sphere, but a single spot (with a permanent light), a small cube slightly in front of the spot, which expands, a blue star advancing in front of the spot and then receding, a semitransparent star, she moves forward and backs off.
Lamp 5: a spot and a small sphere slightly in front of the spot, which expands.
Lamp 6: a spot and a small sphere even closer to the spot, which expands, a semi transparent cone with reflection effects.