Sharpie is the creation of a bored art student.
She threw the piece of paper with Sharpie's design on it away into a trash can with old paint supplies in it.

It was coincidentally the same trash can in which other cast out cartoon creatures had come to life.
He crawled out of the trash can, goopy and rather disoriented because of the rainbow paint now clinging to him.

Sharpie never let his hopes and dreams dwindle after he was thrown away.