Bieber told Radio Disney last week that he uses Gundy's famed "Come after me! I'm a man! I'm 40!" speech as his phone ringtone. Bieber says he watched the video of the 2007 rant "and I thought it was funny so I set it as my ringtone for everything."
On Monday, Gundy's cell phone rang during a news conference and the ringtone was Bieber's hit, "Baby."
Gundy said he changed his ringtone on Sunday because "I figured if he was going to use my ringtone then I should start to use his ringtone. Asked if he's a fan of Bieber, who performed at the Grammy Awards in Los Angeles on Sunday night, Gundy quipped, "I am now."
Gundy joked that he would encourage Bieber to purchase a suite at Boone Pickens Stadium.
"I would prefer that he would come and sing and perform a concert here and buy a suite," Gundy said. "We still have some available."
Gundy's rant came after a column about possible reasons for then-starting quarterback Bobby Reid's demotion appeared in an Oklahoma City newspaper. The coach used his entire postgame news conference after a win over Texas Tech to berate the columnist. It gained national attention and became a YouTube staple.
Gundy spoke Monday while addressing the hiring of new offensive coordinator Todd Monken, wide receivers coach Kasey Dunn and running backs coach Jemal Singleton.