Nuts.

That was the immediate reaction when it appeared a giant yellow peanut M&M would replace the Big Peach during New Year’s festivities at Underground Atlanta.

Hearts rested easy on Monday when the Peach took its rightful place on the tower at the downtown attraction, with assurances that it would drop as per custom.

The brouhaha pointed out the tricky path sponsors tread when underwriting a familiar event. They want to gain attention, but not the wrong kind.

“You want it to be clear who’s sponsoring the event, without having it seem like the event is being taken over and turned into a commercial enterprise,” said branding expert Tim Calkins, of Northwestern University’s Kellogg School of Management.

The giant M&M appeared Monday, sparking questions about whether the native fruit had been displaced by a candy-coated legume. Underground’s initial announcement that Mars Chocolate will be a presenting sponsor of the event, which draws about 100,000 visitors to Underground every New Year’s Eve, did not immediately answer that question. (It merely promised that the drop would be “Powered by M&M’s Peanut.”)

Underground spokeswoman Michelle Lawrence was more explicit on Monday. The mammoth yellow treat will stay at the top of the tower, while the considerably smaller Peach makes its ceremonial descent to mark the transit into 2014. The big peanut will apparently crack open at the zero hour. It’s a good bet that there will be candy inside.

Lawrence said the outcry underscored the fact that this 25th anniversary Peach Drop has loyal fans. “It’s great to hear people are invested in the peach,” she said. “We are going to continue with the tradition.”This year isn’t the first time that the Peach Drop has had corporate sponsorship. AirTran was a presenting sponsor from 2005 to 2009 and was credited in the title.

What is new is that there is a giant effigy of a non-melting (at least not in your hands) candy, perched high above Alabama Street.

Lawrence said Mars approached Underground Atlanta earlier this year with a proposal to collaborate on the Peach Drop as a way to introduce M&M’s “Year of the Peanut” campaign for 2014. Originally Mars hoped to replace the peach with the wise-cracking candy, reasoning that Georgia loves peanuts too.

The answer was no. “It’s important that we maintain the integrity and tradition of the Peach Drop,” said Lawrence. “With them sharing space on the tower, we accomplished what they wanted.”

They certainly accomplished the intent of the sponsor, which was to get attention.

Twitter, Facebook and other social media buzzed with opinions on the matter, many negative. “More corporate sponsorship run (amok),” said one commenter on Access Atlanta.

While some may not like it, sponsorships make for better events, said Ken Bernhardt, marketing consultant and retired Georgia State University professor. Sponsors allow organizers to plow more money into events, recruiting better talent and generating more visibility.

For this year’s Peach Drop, M&M paid for headliner and Grammy nominee Jannelle Monae, an Atlanta native and a hot property. That’s a step up from last year, when Beatles tribute band Abbey Road Live headlined; Tito Jackson was the main attraction in 2010.

Underground Atlanta won’t say how much the M&M sponsorship is worth, nor how much it costs to stage the event, but production and security costs are significant. The City of Atlanta plans to deploy about 250 officers, and state and homeland security forces will also be involved.

Underground hires about 20 bands for the event, which begins at 11 a.m. on Tuesday, Dec. 31, and continues until 3 a.m. the following morning. It drew about 175,000 people last year.

That crowd is ten times the usual number of visitors to Underground, and their economic impact is felt in restaurants, cabs and hotels throughout downtown.

Sponsors improve that bottom line, said Bernhardt, pointing to the success of the Chick-fil-A Bowl, compared to its former life as the Peach Bowl. “It has sold out every year since the Chick-fil-A Bowl started, and it was never a sell-out before.”