you have snuck inside Peach’s Castle to rescue Bowser, return him to his castle, and also return him to his normal size

you tell him to be quiet as to not alert anyone about this, you get him out of the cage, and get out of the castle without anyone ever knowing about this

you jump into a Warp Pipe and it takes you inside Bowser’s Castle. You sit him on the ground and give him a Mushroom to return him to his normal size