The blue on Rebecca's teeth disappears when Whitefeather sends her home (before she could possibly have brushed her teeth or otherwise scrubbed the ink off).
The ADHD medicine that Rebecca finds in the bathroom is not a stimulant or other kind of ADHD medicine, but a medicine for high cholesterol.
During Paula's jazz club number, saxophone notes can be heard while the actor playing the saxophonist doesn't even have his mouth on the instrument.