Sufjan Stevens' bouncy, brassy "Come On Feel the Illinoise!" provides the upbeat soundtrack, creating a pep-rally mood, deepening the campaign's ties to hometown Americana.

"We want to broaden the aperture to show the whole of America—from the wacky to wonderful—and how our guests own their Sonic experience," says Lori Abou Habib, the company's CMO.

The "2 Guys," who yukked it up for eight years in popular ads by Sonic's previous lead agency, Goodby Silverstein & Partners, will continue to serve as brand ambassadors, says Habib. But moving forward, reality rules.

Some might miss their quirky humor, while others, believing the schtick's played out, will applaud the duo's reduced role.

Either way, such a radical change feels risky. Though oddly, the new direction actually seems like a throwback. It positions Sonic as a vital part of the current cultural landscape (updating the Eisenhower-era drive-in experience with a side order of 2020 panache).

In some markets, no doubt, such themes will resonate. And even where the appeal's wholly nostalgic—or nothing but a novelty—the affable spots just might coax viewers to hit Sonic for some Reese's Overload Waffle Cones and oh-so-crispy Potato Tots. (We'll eat them in that order—no apologies!)

"It's not that often you are asked to evolve a cultural icon," says Mother executive creative director and partner Joe Staples. "We of course wanted to celebrate Sonic's insane variety of food, but we also wanted to celebrate the journey and experience you have in your car when you are there. It's a combination no one else can offer."