One of the CIA's most bizarre Cold War efforts was Operation Acoustic Kitty. In declassified documents from the CIA's super-secret Science and Technology Directorate, it was revealed that some Cold-War-era cats were surgically altered to become sophisticated bugging devices. The idea was that the cats would eavesdrop on Soviet conversations from park benches, windowsills and garbage containers. The cat was meant to just stroll up to the sensitive conversations, completely unnoticed. The clandestine cat's electrical internals would then capture and relay the audio to awaiting agents.
The project was funded and work began in 1961. Former CIA officer Victor Marchetti recounts the story of the Acoustic Kitty:
After several surgeries and intensive training, the cyborg cat was ready for its first field test. The CIA drove the cat to a Soviet compound on Wisconsin Avenue in Washington, D.C., and let him out of a parked van across the street. The cat ambled into the road, and was struck by a taxi almost immediately. Five years of effort and over $15 million in spending were reduced to roadkill in an instant. Shorty after its demise a CIA operative returned to the accident site and put the cat's remains into a container to prevent the Soviets from getting their paws on the sensitive and expensive listening devices.
While the memo says that the use of trained cats is possible, it also says that "the environmental and security factors in using this technique in a real foreign situation force us to conclude that for our (intelligence) purposes, it would not be practical."