Which retired American football quarterback played himself in 'Ace Ventura: Pet Detective' and 'Little Nicky'?

The retired American football quarterback who played himself in "Ace Ventura: Pet Detective" and "Little Nicky" is Dan Marino. Marino's appearance as himself in these movies can be attributed to his significant popularity and success in the sport during his career. As a highly-respected and recognizable figure in football, his portrayal of himself added a level of authenticity to the films, creating an enjoyable experience for fans of both American football and popular culture.