His mother was a seamstress and his father a brick mason, and the young Lunadei first developed an interest in acting when at age five, his parents introduced him to the cinema and theater.

The family struggled during World War II, however, and his mother emigrated to Buenos Aires, Argentina, where Gianni arrived in 1950, followed by his father shortly afterward.

His career on the stage flourished, and he worked as a resident actor in the National Comedy for eleven years, and in the General San Martín Theatre for six.

Beyond the stage, he had a turn as Count Dracula in a 1968 made-for-television special starring veteran horror film actor Narciso Ibáñez Menta.

This latter role won Lunadei the city of Mar del Plata's "Star of the Sea" in 1975 with co-star China Zorrilla.

He had a leading role in Manuel Antín's Allá lejos y hace tiempo (Long Ago and Far Away, 1978); but in subsequent years he became known for portraying manic characters in picaresque comedy films and on television.