"Coach" is the latest chapter in Snickers' global campaign "You're not you when you're hungry", based on the insight that hunger can dramatically change your personality. In this spot, an American football team has reached a crucial moment in their game. As they gather around their coach, expecting to be given a game plan, they instead encounter their hungry coach, in the form of comedian Robin Williams—whose hunger has caused him to become loopy and give nonsensical advice. After he's given a Snickers and returns to himself, a hungry cheerleader then becomes loopy, in the form of comedian Bobcat Goldthwait.

You’re not you when you’re hungry” is the global Snickers campaign we launched in 2010. It has come to life in many forms around the world, but most famously in TV commercials that use well-known celebrities to demonstrate the negative effects of between-meal hunger – from Betty White portraying a guy who plays football lethargically, to Joe Pesci respresenting a short-tempered partygoer.

To cast the perfect celebrity, we look for several things. They need to be known and loved by a mass audience. It helps when they have maintained a consistent appearance over time. And most important, they need to be famous for an attribute that is synonymous with hunger-induced behavior.

This year we wanted to focus on the hunger symptom we call “loopy” – the way you act when low blood sugar causes you to feel scatterbrained and unfocused.

No celebrity embodies this symptom better than Robin Williams. Through decades of stand-up comedy, television and movies, Mr. Williams has consistently performed in a way he describes as “legal insanity.” In the space of a 30-second commercial (and a :15 cutdown), his trademark fast-paced barrage of non sequitors would be the perfect way to convey exactly how loopy hunger can make you.

We had two big challenges:

1) Convincing him to star in a commercial. Until now, he had only ever appeared in one—for a video game which he loved to play.

2) While other brands use celebrities as aspirational spokespeople, our campaign put us in the unique position of asking an Oscar-winning A-lister to symbolize “the problem.”

We approached Mr. Williams with a willingness to work collaboratively on a script that felt right for him, along with a screening of the previous spots in the campaign to show him that he was in good hands. He agreed to play the role of the loopy, hungry football coach, worked with us through several collaborative writing sessions, and went above and beyond expectations in performing the script, and in alternate versions, and by improvising dialogue during the shoot

For very little money, the campaign made national press in major cities across the U.S. and brought Snickers into the pop-culture conversation in the weeks leading up to the 2012 U.S. presidential election. People ate lots of candy and voted.