Continuity mistake: During Sullivan and Maguire's gun fight at the hotel, between the fifth and sixth shot Maguire takes at Sullivan, a bullet imprint instantly appears on the trunk Sullivan is taking cover behind, in the top right corner.
Continuity mistake: When Michael Jr. is doing his math homework, he holds his pen between his forefinger and middle-finger. In the next camera view, the pen is between his middle-finger and ring-finger. The books are also in different positions. When camera switches back to the first view, everything is as at the beginning again. (00:04:35)
Answer: He was doing a hot rail. If you heat up cocaine in a glass until it burns, you then inhale the smoke left behind.