The mouse's creation of a ball of string cheese. This impacts rebranding Smuntz String into a business where Lars and Ernie can work where it has the comfort zones they need; Lars pursues taking over his father's business as Rudolf always wanted, and Ernie can work as a head chef as he did at his old restaurant.
While the mouse was responsible for helping out the brothers in their factory, who knows when word gets out that a rodent is present and they'll be shut down for good?
It probably won't happen like that. The mouse is perched on Ernie's shoulder in front of multiple employees, with Ernie even talking to it, and nobody bats an eye. He also mentions an idea of having it appear on television as the factory's mascot—which would give it even more exposure—without any fear of potential consequences, so there probably isn't any real danger.
