Aside from Barbara, everyone, including Professor Grant, appear to be wearing not only the same outerwear but also the same clothing underneath to class on the three consecutive Tuesdays in April. Barbara's outerwear changes: first wearing a buttoned-up white coat; then a daisy yellow blazer with a white blouse and gold necklace on the outside; and finally, an olive blazer with the same blouse and necklace.
At the beginning of the program, Friday tells Gannon that the students don't know that he's a cop because the idea behind the class is that they aren't supposed to know what each other does for a living. The professor wants each student "to react to the person, not the occupation". That's how it is that no one knows that Friday's a cop until he arrests Jerry...and yet beforehand, Barbara discusses pretty openly her work at the hospital.