Adventurers needed to perform experiments.

A scientist created a nondescript grey blob of mass with a modified Intern Regenerator to experiment on it. However, they lost capability to describe its exact effects after coming into prolonged contact with it for unknown reasons, and party was brought in to perform... "creative" tests, while not destroying it. After some time, they realized that contacting it temporarily drained attribute points while simultaneously giving it more definition. With the addition of concentrated genetic material from one of the labs, a skeleton, and an eyeball, it eventually took on human form, although with no knowledge of anything, including itself. Post main game, Nora and Fionna filled out paperwork to get their own identification cards at Red (Intern) level, the lowest available, to potentially come back and visit Grey (as the creation came to call itself).