You were in class doing some assignments. You got stuck on a question, so you asked Aizawa to help you. He explained how to solve the question as you wrote it down in your notebook. After he helped, he started walking back to his desk as you just casually blurt out without a second thought while still writing in your notebook:

"Thanks, dad."

everyone turned their heads to you and looked surprised and flabbergasted since you just said that.