Eric McCormack was not the only actor who was up for the role of "Will". John Barrowman (who later starred on Desperate Housewives) was first being considered by FOX, but didn't get it because he was "too straight" and the role went to Eric McCormack. Barrowman is gay in real-life, while McCormack is straight.
'Will And Grace' Trivia: 7 Amazing Facts About The Show
Sean Hayes, Eric McCormack, Debra Messing and Megan Mullally