The film A Boy and His Dog (1975) is based on a science fiction novel by Harlan Ellison. In a post apocalyptic world a boy communicates telepathically with his dog as they scavenge for food and sex. This dog was probably the pattern for many other post apocalyptic companions to follow.
I've seen things you people wouldn't believe.
Attack ships on fire off the shoulder of Orion.
I watched C-beams glitter in the dark near the Tannhauser gate.
All those moments will be lost in time, like tears in rain.