I think a good shock is one that is outrageous whilst still being believable.
If it’s too big a leap then it seems weird, out of character and more baffling than shocking.
‘He’s retiring to become a monk, what?!? Why?’
If it’s too typical of that person then it’s not shocking.
‘Of course they’re getting married, they’ve been together for 10 years, I’m happy for them but … boring!!’
A good surprise needs to be something you wouldn’t guess whilst still fitting your perception of that person.
Thomas Duggan 