Carrie is a pixl that can carry the player across spikes and can be used to jump on spiky enemies. She was locked up in Francis's Dungeon. To get her, she will give you 3 choices to describe what Francis is to you and then sum it up. Just choose the ones that involve anything nerdy and she will join you.
While using Carrie, Mario can travel slightly faster than while walking, and he can even use Carrie in space for more speed and control. Bowser will also be able to use his flamethrower in midair.
If Luigi's Ultra Jump is used while he is on Carrie he will jump off Carrie before using Ultra Jump.
Carrie folded together (excluding the wings), will resemble a rectangular prism.