Aliens in the Wild, Wild West

The aliens come from an atmosphere entirely different from Earth's. While humans breathe oxygen, it is actually poisonous to these creatures, they require sulfur to survive. This vulnerability is what makes them so fragile during their time in the 19th-century frontier, as the modern-day air surrounding them is toxic to their biology.

When the townsfolk discover the aliens, they see an opportunity for profit rather than protection. A representative of P.T. Barnum arrives to purchase the creatures, treating them as curiosities and commodities. The locals view the aliens as a spectacle that could earn them money, reflecting the opportunistic nature of the era's emerging entertainment industry.

The siblings' constant bickering and fighting triggers a time-travel mishap that unexpectedly drops them into a mid-19th-century western town. The exact mechanics of the time travel are not detailed, but their conflict serves as the catalyst that transports them from their modern suburban lives to the dusty frontier.

The timeline establishes that their fighting directly causes the time-travel incident.

Sara's decision to intervene marks a significant moral shift for her character. Earlier, she is introduced as a rebellious teen who went on a joyride in a stolen car with a convict boyfriend. Her resolve to save the aliens comes from recognizing the clear moral wrong of exploiting innocent beings. The experience challenges her impulsive nature and forces her to act with empathy rather than bravado.

Her earlier reckless behavior contrasts sharply with her later moral conviction.

After successfully returning the aliens to their spacecraft, the ship's mechanism activates and transports the siblings back to the present-day ghost town from which they originally departed. The precise workings of this technology are not explained in detail, but the ship serves as the vehicle for both their journey to the past and their return to the present.

The aliens are described as cute and fuzzy creatures, resembling a hybrid of E.T. and a hairy Yoda. The youngest alien has a voice reminiscent of Elmo. This design choice makes the aliens appear harmless and endearing, which increases the emotional stakes when the townspeople threaten to exploit them. Their vulnerable appearance reinforces the moral message about protecting innocent beings.

The shared mission to protect the aliens transforms the siblings' rivalry into cooperation. Forced to depend on each other to survive in the past and execute the rescue, they develop mutual respect and understanding. By the time they return to the present, their sour relationship has healed into a warmer, more considerate dynamic, with both resolving to support each other rather than fight.

The timeline shows their relationship evolving from constant bickering to shared mission to reconciliation.

Tom and Sara successfully guide the aliens back to their spacecraft hidden in the forest. Once reunited with their ship, the creatures are able to safely board and continue their journey. The siblings' intervention ensures the aliens escape exploitation and return to their own kind, while the ship subsequently returns the kids to their own time.

Oxygen is poisonous to these aliens because they evolved in an environment with a completely different atmospheric composition. Their biology is adapted to breathe sulfur rather than oxygen, making Earth's air toxic to them. This vulnerability is why they must be kept away from human-populated areas and why returning them to their ship becomes urgent.

Tom discovers this weakness when he first finds the spacecraft.