While the Ford Mustang made its debut at the 1964 New York World’s Fair and changed the face of American motoring almost overnight, another vehicle debuted at the same time at the same venue and with the same revolutionary goal, but almost immediately slipped into utter obscurity. (via GM Bison | Hemmings Blog: Classic and collectible cars and parts)
Looks like it is from the Thunderbirds, and has the set of UFO in the background :)
Source: blog.hemmings.com

