I'll Follow You Down

Marika

Erol

Sal

Gabe

Young Erol

Grace

Jimmy / Johnny

Mrs. Moore

Avril

Young Gracie

Aya

Dr. Reynolds

Student

Agent

Lady at Airport

Jeremy

Professor

Asim

Old Woman in Princeton

Hatcher

When the professor dismisses his class and is talking to his grandson, a bashful male student hurries between them and surreptitiously places an apple on the professor's desk. This is an inside reference to a similar bit in 'Raiders of the Lost Ark'.

When the grandfather is explaining to the son what he thinks happened to the boy's father, the grandfather makes a comment to the effect that he doesn't understand it all because he's not 'a specialist in quantum mechanics'. This movie deals with time travel and relativity, not quantum mechanics. Relativity deals with the large scale and quantum mechanics deals with the small scale. The reconciliation of the two has been the holy grail of physics, 'Unified Field Theory'. To object that one doesn't understand time travel because one is not a quantum mechanic is nonsensical. No physics professor would make that mistake.

Young Erol: Dad!

Sal: I need you to be open to the craziest possibilities.

Gabe: Time's up.