Who is that "best boy" in the credits???

Best Boy

AKA: Assistant Chief Lighting Technician, Best Boy Grip, Best Boy Electric
The chief assistant, usually of the gaffer or key grip. In charge of the people and equipment, scheduling the required quantities for each day's work. The term originates from promoting the crew's 'best boy' to supervising, allowing the gaffer and key grip to stay on set and carry out the cameraman's lighting needs. The origin of the term is from "pre-union" filming days when the line between Grip and Electric departments was less rigid. When the head of either department needed another body temporarily, he'd go to the head of the other department and ask him to "lend me your BEST boy". By default the 2nd in charge of either department came to be known as best-boy. This term may also have been borrowed from early sailing and whaling crews, as sailors were often employed to set up and work rigging in theatres. There are no "best girls" per se; female chief assistants are also called "Best Boys".