In the first section of his works called "Free and easy wandering" there is a section where the character Chen Wu tells another character:
Ordinarily a person probably would have written this off as highly imaginative fiction, however I find it quite interesting. First off is the description of the Holy Man, "...with skin like ice or snow, and gentle and shy..." which bears in my opinion a similarity to the classic gray aliens, minus the large black eyes aspect. Then we come to the fact that, he doesn't eat normal food, and rides a dragon which could be an aircraft of some kind, described in terms familiar to the ancient Chinese. Finally we have the possibility of highly advanced or evolved mental powers in the "...concentrating his spirit..." portion. Overall it screams ancient alien to me.
There is also the possibility that it could even be connected to the Dropa stones story, where a supposed race of alien beings landed near the Chinese-Tibetan border and were unable to leave due to some sort of misfortune. After realizing their predicament, they settled in a system of caves and tried to fit in the natives of the region only to have been all, but wiped out by them. In the end they left behind hundreds of stone discs that show signs of advanced engineering.
All this is of course conjecture, but I feel the account in Chuang Tzu's writings make for compelling evidence of possible alien contact in ancient China and perhaps lends more credence to the Dropa story. Maybe the "Holy Man" is even a Dropa?
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The excerpt from the Complete Writings of Chuang Tzu is from an online translation by Burton Watson.