You stepped into a square portal then ended up in a yellow cubic room

You see a massive humanoid, two-dimensional pink shadow with blue eyes moving across walls, floors, and ceilings and covers a major part of the room, you looked up but here are no people

"Hey dude I'm Prismo, a wishmaster and who're you? Are you here to make a wish?"

It seemed like Prismo is the shadow himself, he speaks with a very chill and friendly voice

"You'll only get one wish though, so make it worth it dude!"