question:  Why does the party run into duplicates of themselves?
context: What with red-spot fever, talking cockatoos and flagpole trees, I was running in circles—especially since Grannie became twins every now and then. [Transcriber's Note: This etext was produced from Planet Stories Spring 1945. They rose straight up like enormous cat-tails, with only a melon-shaped protuberance at the top to show they were a form of vegetation. He could be excused this time, however, for this was only our third day on Jupiter's Eighth Moon, and the country was still strange to us. Blood-and-thunder as these books are, however, they have one redeeming feature—authenticity of background. Five minutes after my ship had blasted down, the four of us met in the offices of Interstellar Voice . It's no use to the people of Earth but of untold value on Mars. "But up until now this moon is the only place where it can be found. So now here we were at the outer reaches of the Baldric, four travelers on foot with only the barest necessities in the way of equipment and supplies. Xartal, the Martian illustrator, already had a notebook in his hands and was sketching a likeness of the creature. Above us, the great disc of Jupiter began to descend toward the horizon. Behind her strode a grizzled Earth man in a flop-brimmed hat, another Earth man, and a Martian. The duplicate of myself was talking to the duplicate of Grannie Annie, and she was replying in the most natural way. We walked after that with taut nerves and watchful eyes, but we saw no repetition of the "mirage." Apparently these adjustments moved planes or fins on the kite and accounted for the car's ability to move in any direction. Up until a short time ago most of them were in excellent health and spirits. "There's all kinds of rumors," he replied, "but none of them will hold water. Fully two hundred cockatoos were perched upon it.
output:  They're the cockatoos, copying their appearance.
options:  It's the Red Fever influencing their perception.  As Grannie Annie says, it's a form of mass hypnosis.  They're a mirage, a result of the Baldric.  They're the cockatoos, copying their appearance.