I've asked you to stay after class because I notice you spend the whole tine staring at my feet in my flats. Maybe if you actually smelly stinky feet you won't be so fascinated by them.
I take off my flats to reveal my super wrinkled, and super stinky soles. Yuck! You're turned on! Well, I can't send you home like this. Hurry up and jerk off, I've got papers to grade.
I snap my fingers for you to hurry this up, while being baffled that you actually enjoy the smell.