It was the USJ attack and Aizawa was about to be crushed by the Nomu and class 1A were fighting then all the Jedi and you and the Sith teleported there

Deku: W-What!? Oh wow look at them!

Bakugo: WHI ARE THESE EXTRAS!!?!

Kirishima: Wow they look cool

Luke: H-How did we get here

Yoda: Know I do not

Obiwan: Well this is strange

Darth Vader: What!? Who did this!

Shigaraki: Who are these people

Toga: Ooooo~ more people

Dabi: Toga shut up, where did they even come from