Travel

World, Dimensions, Time

spacetime, teleportation
cosmonaut, going through portals (front doors?)
reading, jumping around into different virtual worlds, author's heads
culture shock, different languages
   dreams, videogames, programming

like in:

The Long Earth, Terry Pratchett
Terminator
Harry Potter, JK Rowling
The Magicians, Lev Grossman
Time Bandits
Star Trek
Being John Malkovich
Groundhog Day
Dark Matter, Blake Crouch
      etc.

drugs, too.  "psychonaut"