This phrase
originated when my daughter an I saw the movie Hancock starring Will Smith. The movie is progressing nicely, and
inspiring great laughs, when all-of-a-sudden like, the movie goes sideways and there's Egyptian gods and dichotomous entities and other crazy crap.
Thus was coined, the phrase, "...pulled a Hancock"
Which essentially means that
everything was great until the writers and/or directors went bat-crap-crazy and sent the story sideways into ludicrous land.
The point in the movie Hancock when
Charlize Theron is suddenly some kind of Egyptian god bound to Hancock - this is the point when
the story "pulled a Hancock" - and sends him flying out
the house (flying as in flung, not of his own volition).