Not/never in somebody’s wildest dreams
Definition 1 of 1
Pro Tip 1/3Unexpected Surprise
Use when something happens that's so surprising, it's beyond what one could even imagine. 
I never in my wildest dreams thought I'd move to another country.
Pro Tip 2/3Strong Emphasis
Shows strong feelings about the unlikelihood of an event or situation. 
She never in her wildest dreams expected to meet her favorite author.
Pro Tip 3/3Positive or Negative
The phrase can refer to both incredibly good or bad scenarios. 
He never in his wildest dreams imagined such a disaster could happen here.