In a new clip, the duo enjoys burgers and fries at the parking lot of an In-N-Out Burger, where they talk about their interest in airplanes. They're then briefly interrupted by an In-N-Out worker named Travis, who brings them chocolate milkshakes.



"Are you with the restaurant?" Letterman asks.

The man hands off a couple of shakes.

Clooney asked, "What is that, is that a milkshake?"

"That is a chocolate milkshake," ascertains Travis.

As Travis walks away after a pleasant exchange, Letterman can't help but tease Clooney.

"I notice you didn't dig down to give the guy a gratuity," he cracks.

On that note, guests reportedly slated to appear on future episodes include Jay-Z, Howard Stern, Tina Fey and Malala Yousafzai.