Sans is the Atlas of the project! Instead of doing "puzzles" with his brother, he'd rather just take a million naps. He eventually starts working with him, and stops being a lazybones... But later, Sans starts to realize the kind of guy Error is..... Because of this, he gets more and more motivated to complete the test chambers, as he wants both him AND his brother to get out of the facility as SOON  as POSSIBLE, before something bad happens...