Sure enough, the Pirates' new middle-infield duo came up with the nickname themselves during Spring Training. Observant fans might already have caught on, perhaps even subconsciously during games at PNC Park.
After each double play the two of them turn at home, the Pirates' public-address system rings out with the beat from Salt-n-Pepa's "Push It," fulfilling a request made this spring by Mercer and Harrison.
"We needed to come up with some kind of name," Mercer said. "We started it."
The Pirates have turned 45 double plays this season, tied for the fourth-most in the Majors, and 20 of them have involved the keystone combination.
When the Pirates traded Neil Walker to the Mets this offseason, they knew they had a qualified second-base replacement in Harrison. He had bounced around the field for Pittsburgh the last few years, but his natural position -- where he played in the Minor Leagues alongside Mercer -- was second base.
"It's nice. He's super athletic," Mercer said. "It's different than it was in the past. You know what you're going to get out of Neil, consistent every time, knowing what plays he could make and what plays he couldn't make. With Josh, I don't even know what plays he can make.
"He's always got me on my toes. He's just so athletic and so explosive. He makes things happen and it makes my job easier."
Mercer and Walker had a nickname, too, for those wondering. But Mercer wouldn't divulge what they dubbed themselves.
"That's still a secret," he said, smiling. "We did have something. It wasn't Salt and Pepper, though, I can promise you that."
It didn't take much time for Mercer and Harrison to get back on the same page. They had to remind each other about some of their habits -- where they like to receive throws at second base, how they prefer to pivot, whether they'll drop to a knee making tags and so on.
"It wasn't much of a difference at first," Mercer said. "It's just kind of rekindling our relationship, what we had in the Minor Leagues."
Adam Berry has covered the Pirates for MLB.com since 2015. Follow him on Twitter @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.