The author of Plot & Structure says any surprising element would work: “A telegram arrives. An alarm goes off. A dog bites. The hero is fired.... Next time you get stuck in your story, make a quick list of things that could happen. They must be unexpected and unplanned. Select one that suggests imaginative possibilities to you.”
For some reason that reminds me of the movie Erin Brokovitch (which was based on a true story). Near the beginning of the movie she is driving and her car is suddenly T-boned. Boy, did that make everything come alive.