The Cast is hanging about in proximity of some historical event, perhaps to make certain it happens the way its supposed to.
Pros:
Literal historic drama, and a mountain of existing time travel fiction from which you can borrow ideas.
Cons:
A mountain of existing time travel fiction where this has been done before. Also may require more actual research than most scenarios.
Fate Value: 4-10
Example: "Welcome aboard the fabulous Lusitania, which of course will sink in 16 hours. None of you are on the list of known survivors, but try not to drown anyway...."