In Pixar's Cars 3, Doc Hudson inspires Cruz Ramirez's racing number.
Cruz Ramirez uses the number 51, the same number associated with Doc Hudson's racing career. The connection becomes meaningful when Cruz learns more about Doc and Lightning's history. Her number is not chosen because she is literally Doc's relative or because she drove his original car; it is a tribute to his legacy.
Doc's 1951 Hudson Hornet was a three-time Piston Cup champion in the Cars storyline. His career ended after a crash and the racing world moved on, but his technical knowledge and experience remain important to Lightning. Cars 3 extends that legacy through Cruz.
The number also creates a visual bridge between the retired champion and the aspiring racer. Cruz's path is her own, however. She is trained in modern racing methods, discovers her own competitive ability, and ultimately demonstrates that honoring a predecessor does not require copying that predecessor's career.