In Pixar's Cars 3, Cruz Ramirez races under number 51.
Cruz is introduced as Lightning McQueen's trainer at the Rust-eze Racing Center. Although she initially works in a coaching role, she has racing ability of her own and becomes increasingly important as Lightning confronts the rise of Jackson Storm and the changing standards of professional competition.
Cruz's number 51 pays tribute to Doc Hudson, the former Fabulous Hudson Hornet whose racing number was 51. Doc becomes Lightning's mentor in the first Cars, so Cruz's eventual use of the number connects her to the film series' themes of succession and legacy.
This number is easy to confuse with Lightning's 95, Jackson Storm's 20, or The King's 43. Cruz's final competitive identity is also linked to a yellow race-car design rather than her earlier yellow training vehicle. Cars 3, released in 2017, uses her story to show that racing talent can emerge from an unexpected place and that a champion's legacy can continue through a new driver.