At 21 minutes, the dark water mark patch on Will's shirt changes side and in volume from shot to shot through out the scene
Will McAvoy says, "I only seem liberal because I believe that hurricanes are caused by high barometric pressure and not gay marriage." Hurricanes have low barometric pressure, not high pressure.
Will says his date walked into his apartment with a "loaded thirty-eight caliber Walther PPK pistol". Walter does not make the PPK in .38. They do make it in .380 and .32.