Starring in Comic:

Security Guard Silent

Luigi "Superstellar-Up!"

Dr. Eggman "Conquer-Up!" = Dr. Golden "Prepare-Up!"

The Secret of Fierce Forces Reveal:

Dr. Golden "Prepare-Up!" after: "Evil Realized" Ending,
has received the ability to swap into human form, which he wanted to regain
(after the tragic event that happened in Five Nights at Sonic's 3).
He can change into his alter aspect as much as he want and when he want:
Dr. Eggman "Conquer-Up!"