Watch The Big Bang Theory Season 4: Episode 12: The Bus Pants Utilization Online where we shall watch how Sheldon would try to assert his superiority on his gang in a project that happens to be the brainchild of Leonard. This is what happened.
Leonard comes up with a great idea for an phone app and the guys all pitch in to help. When Sheldon becomes too controlling, Leonard fires him. Penny finds Sheldon by himself in the hall, she invites him to work with her on an app of their own.
Quickly annoyed with him, Penny begs the guys to take Sheldon back. When they refuse, she convinces Sheldon to practice his sarcasm and apologize to Leonard so he can work with them again.
