BURBANK, Calif. (AP) — What’s real estate mogul Donald Trump got against President Barack Obama? The president says it’s an old grudge that goes back — way, way back — to their childhood days in Kenya.

“We had constant run-ins on the soccer fields,” Obama told “Tonight Show” host Jay Leno during a tongue-in-cheek knock on Trump Wednesday night. “He wasn’t very good and resented it. When we finally moved to America, I thought it would be over.”

Trump became a leading voice in the “birther” movement, the discredited but very much alive conspiracy theory that Obama was actually born outside of the U.S. and isn’t constitutionally eligible to be president. Earlier Wednesday, Trump offered to donate $5 million to the president’s charity of choice if he would release his college and passport records.

Wisecracks aside, Obama told Leno that he has never actually met Trump.

When Leno asked Obama if he was glad the presidential debates are over, the president responded, “You know, I was sort of getting the hang of it.” Obama, whose performance in the first debate was widely panned, said he didn’t do an effective job of energetically outlining the contrast of visions between him and Republican Mitt Romney.

Part of the problem with a debate, Obama said, is that it’s not a natural way of communicating — having an argument with someone as you sit next to him.

“Well,” Leno said, “you’re married.”

Obama shot back: “But the difference is, with Michelle, I just concede every point.”

Asked which team he was backing in the World Series, the Detroit Tigers or the San Francisco Giants, Obama managed to get in a dig at Romney: “I will say, I’ve spent a lot of time in Detroit lately, and I didn’t want to let go Detroit go bankrupt. So in this particular World Series, I might be a little partial.”

Watch the full interview on “The Tonight Show” below: