Gratton (nicknamed "Gratoony The Loony" for his bizarre actions both on and off the ice) began his WHA career in 1972 with the Ottawa Nationals. Gilles would also spend time with the Toronto Toros. His brother, Norm Gratton was a professional NHL player as well. In the National Hockey League, Gratton would play with the St. Louis Blues and New York Rangers. He is perhaps best known for his goalie mask, which was an adaptation of his astrological sign, Leo. However, Gratton states that he got the idea from a picture in a National Geographic magazine that he was reading on a plane flight. According to Gratton, "It's not a lion mask at all. It's a tiger." Some people believe that Gratton would growl at opposing players on the ice and once hissed like a cat during a fight.