Maybe it was the time a giant toilet ran across Mile High Stadium to a stunned crowd, getting tackled by a security guard as the scoreboard blared: Stop Running Toilets.

Or maybe it was when professional landscapers and horticulture professors wrote disgruntled letters about billboards and radio spots that joked, “Grass is Dumb.”

At some point in the past decade, Denver Water’s signature orange box asking customers to Use Only What You Need became advertising legend in the metro area, winning countless awards, prompting dozens of requests to buy the rights for the campaign, and even eliciting interest for use on specialty license plates.

The campaign is coming to a close this year, making way for a more broad-range message that will go beyond conservation and focus on other issues, including water quality, recreation and long-range planning, among others. It’ll still be unexpected, clever and fun, but it’ll be more individualized and make better use of the digital world. Think less billboard, more hashtag.

Still, the Use Only What You Need catchphrase will remain one of a kind.

“It’s the best advertising campaign this city has ever seen, in my opinion,” said Trina McGuire-Collier, assistant director of Public Affairs, who oversaw the campaign since its inception. “You didn’t expect a government agency to do and say the things we did.”

The Use Only What You Need campaign began 10 years ago, just as the region was recovering from a debilitating drought. Denver’s Board of Water Commissioners challenged customers to reduce their use 22 percent by the end of 2016, a massive undertaking that required an attack on several fronts, through audits, rebates, rates and, of course, advertising.

“We had to cut through the clutter,” McGuire-Collier said. “The drought had gotten our customers’ attention, and we had to strike while they were watching.”

So every year, Use Only What You Need set out to shock Denver Water customers. (Almost) naked people walked through crowds with an orange sandwich board that read: Use Only What You Need. A taxi stripped down to just what was needed to be street legal — basically headlights, tires and a steering wheel — appeared at community events with the same simple, but prudent, message.

Soon Denver Water started pairing taglines with Use Only What You Need to help customers focus their conservation efforts with tangible actions. “Grass is Dumb. Water 2 minutes less. Your lawn won’t notice.” Or “Man’s Time of the Month: Pick a time every month when you do your man thing and adjust your sprinklers.”

“It created this legacy, that every year the industry and our customers were waiting to see what we’d do next,” McGuire-Collier said.

It was modern, often outrageous, and sparked a conversation throughout the city. It also worked.

Customers reduced their water use by more than 20 percent in the last 15 years, despite a 15 percent population increase. “It was the perfect timing for that message,” said Greg Fisher, manager of demand planning, which tracks customer use patterns. “It was just the root of all success we’ve had in conservation.”

It’s impossible to quantify how much of that reduction came from advertising versus rates versus rebates versus the dozens of other methods that encouraged customers to use less. But the campaign certainly had an impact.

Use Only What You Need made people think twice about their water use, said Jeff Tejral, manager of conservation.

“The culture has since changed and water use has changed,” Tejral said. “We need to capture that success and move forward.”

Now the push will be to create a two-way dialogue with customers all year long, instead of only during irrigation season. It’ll help people see Denver Water as experts while teaching them about what their water utility has to offer, said Kathie Dudas, Denver Water’s marketing manager.

At the recent opening of the rail line to Denver International Airport, for example, Denver Water parked its water trailer at Union Station and handed out cups of cool tap water to incoming visitors. Several people cooed about its taste, asking where they could buy it.

“We can’t keep talking with one message, because now the portrait is bigger.” Dudas said. “But you can’t follow Use Only What You Need with corporate speak. We’ve raised the bar for ourselves, and we must set new heights with our future campaigns.”