Django Reinhardt played his incredibly fast improvised lines using only two functional fingers because his ring and pinky fingers were fused together after a fire.
Beato recounts how Django Reinhardt, a foundational figure of Gypsy Jazz, lost use of two fingers in a fire yet still produced astonishingly fast, fully improvised guitar lines.
transcript
Rick Beato: One of the things about Django is that he was in a fire, and he had two of his third and fourth finger, so his ring finger and pinky were essentially melted together. He had no use of them... a lot of these incredibly fast lines, he's just playing with two fingers. And it's amazing.