question:  How was Antlers Park able to fool Ezra and Billy-boy into believing Grannie Annie was with him?
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. Grannie Annie strode in the lead, her absurd long-skirted black dress looking as out of place in this desert as the trees. If my calculations are right, we've hit it at its narrowest spot." Blood-and-thunder as these books are, however, they have one redeeming feature—authenticity of background. Grannie Annie was the original research digger-upper, and when she laid the setting of a yarn on a star of the sixth magnitude, only a transportation-velocity of less than light could prevent her from visiting her "stage" in person. He was an old prospector Grannie had met, and he had become so attached to the authoress he now followed her wherever she went. As for Xartal, he was a Martian and was slated to do the illustrations for Grannie's new book. And then I was shaking hands with Antlers Park, the manager of I. V. himself. Antlers Park flicked the ash from his cheroot and shrugged. Then it was found that this ore, Acoustix, revitalized their sounding apparatus, and the rush was on." 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. And then all at once Grannie stopped again, this time at the top of a high ridge. Attached to its hood was a taut wire which slanted up into the sky to connect with the kite. Five minutes later Grannie was shaking his hand vigorously and mumbling introductions. Occasionally he touched a stud on an electric windlass to which the kite wire was attached. Apparently these adjustments moved planes or fins on the kite and accounted for the car's ability to move in any direction. "There's all kinds of rumors," he replied, "but none of them will hold water. Fully two hundred cockatoos were perched upon it.
output:  He was using one of the images from the birds as an impersonator of Grannie Annie
options:  He was driving the kite car too quickly through the sand to clearly see who the passenger was.  He was using one of the images from the birds as an impersonator of Grannie Annie  He was a skilled mastermind with tendencies that could trick anyone into believing him  His vehicle was equipped with technology that could infiltrate the invention by Baker