Task: Story Composition
Input (English): Premise: I used to love playing pranks on Billy, my older brother. 
 Initial Context: One day I got a black rubber snake. 
 Original Ending: I put the snake in Billy's bed and waited in his closet. Billy came in and pulled back the bed sheets. I laughed when Billy screamed and fell backwards from the snake. 
 Counterfactual Context: One day I got a black rubber spider.
Output (English): I put the spider in Billy's bed and waited in his closet. Billy came in and pulled back the bed sheets. I laughed when Billy screamed and fell backwards from the spider.