Director: "Ok, extra number 47, 'mad old woman'... that's you Bert. Walk from right to left acting mad please."
Bert: "Ok guv... how loony do you want it?"
Director: "Completely off the wall, but nothing overtly physical, you're an old lady after all - that's your motivation."
Bert: "How about I pretend I'm on the telephone? That would be pretty loony because there's no wires or a handset!"
Director: "Just the ticket!"
That's the trouble with films... people act in them, it doesn't have to make sense. I think I've pretty much covered the bases without diving off the edge of reality to the extent of time travel.