Because of the size of the statue, the Bolognese affectionately call "the giant" (Żigànt in bolognese dialect).
The statue was sponsored by Cardinal Legate of Bologna, Carlo Borromeo.
Love the Bolognese often indicate a particular view of fountain, not narrate their disrespecting that would fulfill Giambologna Neptune with larger genitalia but the Church forbade him. The sculptor did not surrender, though in fact he designed the statue so that from a particular angle the thumb of left hand brim of Neptune seems to sprout directly from the lower abdomen, causing him to suggest (built) the genital; the same proof, is shown to tourists, a stone pavement, also called black "shame" in a precise point in Piazza del Nettuno that facilitates vision.
The Trident symbol of Maserati, automaker founded in Bologna, was taken from that of the fountain.