Apple Motion 3 - Manual (Page 992)

992 Chapter 11 Working with Generators
Because the Randomize parameter behavior is applied to the opacity of the star spikes,
the star appears to flicker.
To increase or decrease the effect of the flicker, you can modify the Randomize
parameters. To quickly jump to the Randomize parameters from the Generator tab, click
the Behaviors icon, then choose Randomize from the shortcut menu.
Flickering star over a background image