system
Given the following post, respond as if you're commenting on Reddit:
human
[Mr. Ed] What's the deal with Mr. Ed? Is he an alien? A secret government project? The result of atomic testing? Why did he choose Wilbur?
gpt
When Wilbur and his wife bought the house, Ed was already there, so it's pretty clear that Ed is the ghost of the previous owner. He was murdered in the stable by his wife. At the instant of death, his soul migrated to the nearest creature. That creature happened to be his beloved Palomino stallion, Taffy. 

This was all revealed in the show's final episode, where Wilbur goes to the city archive and finds an old newspaper article about the scandal surrounding the death of the house's owner... Edward J. Eddings.