Universal Pictures studio executives weren't sure of what to make of 12 Monkeys, a time-travel film which Terry Gilliam had directed from a script by David Peoples and Janet Peoples. Later the film would be a huge hit, but before its release, a test audience was confused by the ending. So, at the executives' insistence, a one-shot scene was added to the end: Peters (David Morse) and the future scientist in the plane.
Astrophysicist [commisserating with Peters over what had happened in the terminal
before they boarded]: You might say that we're the next endangered species — human beings.
Dr. Peters: I think you're right ma'am. I think you've hit the nail on the head.
Astrophysicist: Jones is my name.
[Shakes his hand]
Astrophysicist: I'm in insurance.
The execs thought this would make the ending less ambiguous. But Gilliam and the writers made sure the scene could STILL be interpreted two ways, as "the post-apocalyptic future that Bruce Willis' character Cole remembered is real" or "Cole imagined it." Each time I saw 12 Monkeys in a theater with an audience, several people chuckled at the edge she gives her line "I'm in insurance." That line could be straightforward; that line could be an ironic, telling joke. The woman could be an astrophysicist from the future; the woman could just be some woman Cole saw in the terminal before he died, and whom he incorporated into a delusion. Could. Could. Could. Heh.
I learned this from the film's composer, Paul Buckmaster, in a 1996 phone interview I did for my UO Honors College thesis. He explained he'd needed to add a few bars of music to accommodate the extra shot. He also chuckled when he told me about it.
As much as I liked, say, Jacob's Ladder or the director's cut of Donnie Darko, sometimes a little more ambiguity is good.