The McDonnell XF-85 Goblin
This tiny little plane was better known as a "parasite fighter." This meant that it would latch onto a larger aircraft and deployed when said aircraft went under attack. In theory, this would work just fine. Sadly, in practice, it was totally useless.
Such a tiny plane was absolutely no match for any opposing force. It was quickly outgunned and outmatched by literally any standard fighter jet. The Goblin line was quickly scrapped and they went back to the drawing board.