His giant, walrus-style moustache is McDonald's most defining physical characteristic and helped him become an iconic figure in the sport. He developed it in 1974, spending the summer seeing what kind of beard he could grow. Knowing that the Maple Leafs did not allow players to maintain beards at the time, he settled on what he described as a "normal moustache" once he returned to Toronto. Some time later, he was inspired by baseball player Sparky Lyle's moustache and chose to grow one in a similar style. It became a symbol for the Flames as some fans took to wearing fake red moustaches during playoff runs. Razor manufacturers offered endorsements if he would shave it, which he refused.