There is a wonderful way to get students to think about "What might have happened if…" and I have always loved this activity. Over the years I figured out that the best thing is to print enough sheets of each page to divide them up and pass them out so no two students get the same story. That way I don't get bored reading them. Also, I found that some days I just want my students to come up with their on "What if..." about the chapter we just completed.
You can never get enough of these. Every one brings its own unique ending. There are over 51 + ideas/"What if…" here plus a sheet of blank ones for your students to come up with their own. Some of the best you may email me for future lists at firstname.lastname@example.org
I have from way back in our history to more recent ones.