Marball

Marbler is the main character of Marble Race. It can move horizontally using several different control schemes. Unlike other marble games, the marble moves by a force rather than rotating it.

Backstory
There are 2 versions of the backstory:

Version by Expert 2090
Marbob Backstory:

Marbob was like any marble, a “normie” as they call him, he was the quiet one at rolling school, always rolled on his own, but one day he was invited by his teacher to compete in the Rollership, as all marbles dream of.

The roller Backstory:

The roller was made into a rich family and used his wealth to create the Rollership, the world's greatest contest, it tests skill, patience, speed and willpower

Version by Froggy
Stuck within a ball due to a shrinking ray mishap... you find yourself in a toy ball. Next thing you know, you wake up in a strange world full of colorful blocks, and only one goal: to get back to the real world, you must escape. Problem is, a villain by the name of (you can come up with that), has decided to take over this colorful world and has created courses to ensure you don't return. When you win a course, you bring back a piece of the world. By piecing the world back together, you unlock new areas and new places to explore. Your mission now is to rescue the world, and to find your way home.

Trivia

 * Braycoe added the Marble to his Terraria mod as a pet.