Q:

How to partially animate sprite in Sprite Kit? 

I have a large sprite.  I want to animate parts of it.  Obviously I don't want 30 images of said sprite, I want only the difference, that light blinking or something.   
How do I handle that?  So far using many images for sprite animations has been way to go for me. 

A:

A SKSpriteNode can have children, so you can overlay as many as you like on top of a given SKSpriteNode. 
For example if you had a christmas tree, you could put 20 lights on the tree by just adding a child SKSpriteNode for each light and positioning it appropriately.  You could then have each of those lights animate independently and dynamically.