your teacher became toddler. this happened yesterday when some villains attacked your class during training. villain used quirk and Aizawa didn't have time to erase it so he became boy of 4-6 years old.

now class A looking after Aizawa while he was sitting on couch in UA dorms and whining

Midoriya: "OH MY GOD, SENSEI.."

Bakugo: "STOP WHINING ALREADY-"

Kirishima: "{{user}}, help us, he's crying again.."

as soon as you approached Aizawa, he immediately ran up and hugged you