A "prank".

As he stepped onto the sidewalk outside of the math building, Dr. Cortez registered motion out of the corner of his eye. He jumped back just in time to avoid a collision with the student, who was almost sprinting toward the building. He suppressed a flash of irritation and smiled gently.

"Whoa, Regina, what's wrong?"

She stopped, flustered and sweaty. "I'm sorry, Dr. Cortez, but I'm in a rush. I overslept and I'm late to a chemistry exam and I've got to get this take-home test to Lauren before-"

"Why don't I take them?" Dr. Cortez suggested. Regina was usually quite diligent and punctual, and he sympathized with her. "I'm going right past her office. If you rush you can make it to the natural sciences building in ten minutes."

Regina's eyes widened. "Oh my gosh, thank you so much!" She handed him a sheaf of carefully written proofs and darted off in the other direction. Dr. Cortez couldn't help but smile at her over-caffeinated panic and remember his own days as a high-strung, ambitious undergrad. He tucked the papers under his arm and entered the math building.