Do the anything call leaving off the final Extend, then do a full 
  Chain Reaction.
The anything call is usually a Scoot Back variation of a Tagging call.
- For example,
- 
  Flip Reaction: 
  From Parallel Waves.  Flip Back 
  Centers To A Wave  
  then all Chain Reaction. 
- 
  Tag Reaction:  
  From Parallel Lines. 
  Tag Back  Centers To A Wave  
  then all Chain Reaction.
- 
  Load The Boat Reaction:  
   From  Facing Lines (or R-H Tidal Wave). 
  Load The Boat  Centers To A Wave  
  then all Chain Reaction.
 See also Tagging Calls
Notes:
- 
For Tagging calls, there is an unspoken 'Back' (Scoot Back) in them
    (e.g., Tag Reaction means Tag Back Reaction).
- 
The outsides should adjust to form an In-facing Couple before doing the
    Chain Reaction.
- 
Don't rush this call!  Teamwork is required for successful completion.
    Wait for all dancers to form the 1/4 Tag formation before
    starting the Chain Reaction.
 Examples: 
 Variations: Instead of Reaction, the caller may give another call such as
Chain Reaction [A1,C1] (Lee Kopman 1975):
 From an applicable Generalized 1/4 Tag.
  Very Centers and the directly facing Outside dancers Pass Thru as the End
  of the Center Line Counter Rotate 1/4 (on the Outside); Centers of each
  side Hinge; Center 4 Star 1/4 as Outsides Trade; Those who meet
  Cast Off 3/4 as Others move up (Phantom Hourglass Circulate).  
  Ends in Parallel Lines | Waves.