Chicago Police Superintendent Eddie Johnson has presided over a conveyor-belt of graduation ceremonies during Mayor Rahm Emanuel’s two-year policing hiring surge, but Tuesday was different.

In fact, it was, as Johnson put it, “one of the most special days of my entire life.”

Among the 218 new police officers taking the solemn oath at Navy Pier was Daniel Johnson, the former teacher-turned-cop who donated a kidney to his dad and gave the superintendent the gift of life.

On Tuesday, the elder Johnson did what he promised not to do: recognize the emotional moment from the podium and ask the son who had turned the tables and become his father’s hero to stand and be recognized.

When Johnson crossed the stage, he got a bear hug from the dad who is now his boss.

“I’m not just here as superintendent. I get to stand before you as a dad watching my son follow in my footsteps. I promised him that I wouldn’t do this. Matter of fact, where are you out there? Raise your hand so I can see you,” Johnson said as the audience of family and friends applauded.

“I’m so incredibly proud of the young man you have become. Since you were a little boy to when you decided to become a schoolteacher and now, a police officer, you have embodied the meaning of service. You always were centered around helping and giving back to others. And that includes helping me.”

If there was anybody in the audience who hadn’t already heard about the kidney that Daniel Johnson donated to his Dad, Eddie Johnson told the story once again.

“For those who don’t know, I’m standing here today because of Daniel … Daniel was selfless enough to give me the gift by donating his kidney to me last year,” the superintendent said to another round of applause.

“I still remember the night he was born. He came into the world with one eye open. Now, he has both eyes open. Daniel, I love you very, very much. I don’t think there’s words strong enough to describe how proud of you I am. I couldn’t have went to a store and picked a better kid.”

Johnson then passed the baton to Mayor Rahm Emanuel, who picked up on the emotional family theme.

The timing was perfect. The normally detached mayor is already a basket of emotions because of what’s going on in his own family.

“In about two days, Amy and I are gonna become empty-nesters. You don’t have to get emotional. I’ll do that,” said Emanuel, who will spend Labor Day weeked taking his youngest child to college.

“The supe and I talk about this often. That you raise your kids for this moment where they can fly on their own. You’ve given them all of the struggles and sacrifices and imbue them with all the values you want. And then, you watch them become the young men and the young women you’ve always hoped and dreamed and struggled for.”

Emanuel told Johnson: “I know how important this is to you, superintendent. Thank you for sharing yourself and your family with us as a city.”

The mayor made no bones about his own emotional struggle.

“As we’re [becoming] empty nesters, I try to convince my wife, ‘This is what we’ve worked our whole life for. We should be proud of this.’ Then, I go upstairs in a fetal position and cry all by myself,” Emanuel said.

The 218 police officers in Tuesday’s graduating class are 69 percent minority. Twenty percent have a family member in the Chicago Police Department.

Also graduating Tuesday were 111 newly-promoted detectives sorely needed to boost Chicago’s dismal clearance rate for homicides and shootings.