Reddit co-founder Alexis Ohanian and his wife, the tennis star Serena Williams, make headlines not just for their entrepreneurial and tennis wins--but also for their frequent heart-melting romantic gestures. When he proposed marriage, she posted an aww-inducing poem on Reddit. He Snapped his late-night grocery-store runs during her pregnancy. And this week, he posted on Instagram and elsewhere photos of four billboards he'd purchased, featuring photos of their baby daughter and declaring Williams the "Greatest Momma of All Time."

With this last gesture, though, there was an ulterior motive. Ohanian hinted at it in an email blast he sent out about the billboards, by including a link to AdQuick, a Los Angeles-based outdoor advertising startup.

Ohanian's investment firm, Initialized Capital, invested in AdQuick in July 2017. Turns out, Ohanian had recently been looking for an excuse to eat his own dogfood. What he actually said is this: "I was looking for an excuse to dogfood an Initialized Capital portfolio company." In startup parlance, "to dogfood" is to use your own product; say, a company that markets software should employ that software internally.

"I was trying to come up with something to put on a billboard," Ohanian told Inc. It was a chin-scratcher--but one day the answer dawned on him. And maybe drooled on him, for good measure. He was sitting with his daughter, Alexis Olympia Ohanian. "The answer was literally in my lap--Junior."

Ohanian decided to use photographs of Olympia on the billboards, timed to Williams's return to competitive tennis, which is slated for next week in Indian Wells, California, at the BNP Paribas Open. He let Junior help--perhaps lending to the particularly adorable amateurish design. "Olympia also helped pick the photos based on how intensely she grabbed my phone and tried to eat it when I showed her a particular picture," Ohanian said.

AdQuick helped Ohanian locate the billboards, plan a strategy for launching them, and purchase space on four billboards on I-10 outside of Palm Springs, not far from the tournament.

AdQuick was founded in 2016 by former executives of grocery-delivery startup Instacart. AdQuick aims to help clients looking for outdoor advertising not only purchase the space, but also vet locations and analyze the results. "It aggregates the widest variety of inventory nationwide, allows advertisers to book online, and helps close the loop on campaigns, with hard metrics on impact and results," co-founder Matt O'Connor told Adweek.

AdQuick has already worked with companies such as Lyft and Peloton. It raised a seed round of funding in July, from Initialized and other firms, that totaled $1.1 million.

Ohanian is no stranger to outdoor advertising or stunt marketing for ideas he holds dear. In 2014, he crowdfunded and placed large advertisements around the Washington, D.C., area, protesting proposed net-neutrality rules. In 2012, he used a tour bus to promote open-internet initiatives, and purchased a billboard outside a Texas legislator's office to protest a federal bill that Silicon Valley startups believed could throttle the flow of information online.

His latest effort are as much ads for a billboard company as they are a romantic gesture--and Ohanian admits his copywriting skills might need some polishing before he tries again. He says his wife, who has won a record 23 Grand Slam tennis titles, is "already the G.O.A.T. And while G.M.O.A.T. doesn't have quite the same ring to it, maybe it'll catch on."