This is my son’s all-time favorite episode of Land of the Lost, and I understand why.
It’s a unique and interesting puzzle, and part of the reason I love Land of the Lost so much. This episode harks back in some crucial to the great entry "Elsewhen" from the first season, written by Dorothy Fontana, in which Holly met her future self. That future-self, named Ronnie/Rani informed the girl that there would come a time when Holly would be alone in the Land of the Lost, without her father and brother.
“The Pylon Express” is such a fun and imaginative show -- and my son enjoys it so much -- because of Holly’s colorful and extended trip through time and space. The episode takes her to a snowy mountaintop, to the world of that strange bouncy thing (a robot?) and to a terrifying world where a giant machine seems to be absorbing materials from the atmosphere. It looks like a malevolent vacuum cleaner crossed with the Martian war machine from the Pal version of War of the Worlds (1953).