Everyone's past self came back for a day, when it was the most important time of their child hood

Mina painting her little self's nails hot pink. Her little self smiling and giggling, asking so many questions. Kirishima shows his little self all the cool things he can do with his quirk. Deku was calming his younger self down who had just been named as quirkless. Todoroki's just stared at his younger self in confusion as his younger self cried after his mother poured water on his face. Bakugo fighting with the little him who just got his quirk. Etc... that's when your little you appears