Based on the book of the same title by Blake Crouch.
Several times a black cat can be seen throughout the multiverse, signaling mortal danger.
"It's a Wonderful Life" is shown on the theater marquis.
Jasons surname, Dessen, is a German Pronoun. (relative or demonstrative) meaning whose, of which. And quite fitting regarding his journey of which universe he belongs to.
Author of the novel this series is based upon, Blake Crouch, is a writer on this series.