It is a kid's show. The main characters' outfit is modelled after Japan's iconic recovery workers (stark orange and blue), a compliment of their heroics echoed in fiction.

This character can clone himself hundreds times to help others, with art often mirroring the thousands of recovery workers seen in actual event footage.

My comment intended to link back the image of childhood heroes as corporeal selfless adults

It's a technique to temporarily make one or more duplicates of your body which can move independently and have your memories/abilities. A strong enough hit will dispel them, or the user can do it manually, after which the memories of what the clones did return to the user.

The usage here by GP might just be because everyone looks/is-dressed the same and is working in unison, and since they're Japanese, anime comes to mind. In the show, Naruto often uses shadow clones to pull off more complex techniques, throwing himself, having them take turns punching/kicking, or in the case of the rasengan he divides the work of controlling the ball of chakra since he struggled to do it successfully by himself.

That is the reference