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 National Hockey League (NHL) player as well. In the NHL, 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. Gratton played with the Nationals for one season in 1972 before moving to the Toros in 1973, until finally breaking into the NHL in 1975, ending his career with the Rangers in 1977.
Throughout his career, Gratton has been known for his eccentric personality and outspoken character, often drawing the attention away from his talent. While playing in the WHA, he once hurled insults against the opposing team's fans in San Diego ahead of a playoff game. Legend has it that Gratton once told his teammates he was reincarnated and had once been a soldier in the Spanish Inquisition. He may also have believed that he was an executioner who had stoned people to death and was fated to be a goalie as punishment. In a game with the Toronto Toros of the WHA, he refused to play because the moon was in the wrong part of the sky, thereby not lined up with Jupiter. He later mentioned he did so to protest against the firing of coach Billy Harris. 
On THN.com, he was voted to have the 6th scariest goalie mask.
- "New York Rangers Legends: Gilles Gratton". Nyrangerslegends.blogspot.com. Retrieved 2014-01-08.
- The Hockey News. Greatest Masks of All Time. Duff, Bob. Gilles Gratton. Pp 89–90.
- "Top 10: Scary goalie masks". THN.com. October 31, 2008. Retrieved 2009-05-29.
- Legends of Hockey http://www.legendsofhockey.net/LegendsOfHockey/jsp/SearchPlayer.jsp?player=18535
- Zinser, Lynn (December 13, 2006). "Goalies Gone Normal: A Little South of Sanity". The New York Times.
- McGrath, Charles (February 21, 2013). "How Come Martin Brodeur Is Still So Good?". The New York Times.
- Radio-Canada - Que sont-ils devenus? Gilles Gratton http://www.radio-canada.ca/sports/hockey/2009/10/29/002-mardi03-gratton.shtml
- Zinser, Lynn (December 13, 2006). "Goalies Gone Normal: A Little South of Sanity". New York Times. Retrieved 2006-12-13.