In the early blocking stages of animation for Ending of the End part 2, Marble was actually in the place of Maud. Most notably shots 61, 64, and 66. She's even seen with Mud Briar the way Maud is in the final version of the episode. My theory is that the reason for this is that Maud and Marble share the same initials and were swapped out with each other due to a mistake. Maud's initials on her rig are also notably written as "MDE" instead of "MP" because of this.

Coco Pommel also appears in an even earlier version of shot 60, not even making it to the animation stage. But if I ever post her full turnaround, it'll most likely be from her updated appearance there instead of her season 4-era rig found in Slice of Life.