Card "stack" and targeting in Unstable Unicorns- Irrelevance of a defensive Super Neigh
http://unstablegameswiki.com/index.php?title=Neigh,_Neigh%27d,_Neighable,_Neighing

In Unstable Unicorns the stack is literally a stack.  The card being played is placed on top of the card it is responding to.  Therefore the only card targetable is the one on top of the stack.

The Super Neigh is the end of the stack and the entire stack will then resolve.