Stallone began his career with uncredited roles in films such as 'The Square Root,' 'Downhill Racer,' and 'M"A"S"H.'

He appeared in films like 'The Party at Kitty and Stud's,' 'Lovers and Other Strangers,' and 'The Sidelong Glances of a Pigeon Kicker,' often in uncredited or minor roles.

Stallone continued to work in various films, including 'Bananas,' 'Klute,' 'What's Up, Doc?,' and 'Death Race 2000.' He also worked odd jobs, such as cleaning lions’ cages at the Central Park Zoo and ushering at a movie theater.

He gained some recognition with his role in 'The Lords of Flatbush,' which shared lead billing with Henry Winkler.