Interesting fact:
The Characters from Maniac Mania that have changed to Fiercy Forces version, became Silent's "Realistic Imagination" and are connected to her, once she has accepted the game rules made by Dr. Golden.

What does that mean?

Among others, Characters that were an imaginations of other Protagonists from the previous installations, such as Luigi (FNaS 4) who created from his fear: Nightmaric.

Nightmaric, now as Nightmaric "Spooky-Up!" has became Silent's
"Realistic Nightmarish Imagination" and that is why he looks different.

It was a part of the Evil Plan of Dr. Golden "Preparation". So that the Characters would increase their level and become more dangerous (Including, among other things, that by Silent's memory, some of Characters have partially regenerated, mainly: Salvage Sonic has changed into Salvage Sonic "Storage-Up!" so he has his left hand back), but also so that they could not be forgotten.

That is why these Characters are so attached and happy to see the Heroine, even that Silent the Protagonist (Night Resistance) and Clones, Animatronics, Phantasms
(Evil Empire) are on opposite sides, that is why they try to imprison Silent by force to keep her forever.
*A partial explanation of the Plot in Fiercy Forces*