When Donald Trump declared on Wednesday that his “surprise announcement” about President Obama was actually just a plea for him to make his college and passport records public, many of those watching thought it was a joke.

But Trump was very serious, and that in itself has garnered several jokes at his expense. Obama himself appeared on “The Tonight Show” afterward and told Jay Leno that the bad blood between himself and Trump began when they were growing up in Kenya, much to the delight of the audience.

“We had constant run-ins on the soccer field,” Obama said. “He wasn’t very good and resented it. When we finally moved to America I thought it would be over.”

Letterman took his own jab at Trump in the form of a Top 10 List, which he named “Lame October Surprises”:

10. George H.W. Bush admitting he’s the father of George W. Bush.

9. Jimmy Carter’s confession that he’s cheated at Scrabble “in his heart.”

8. John McCain accused of driving under the influence of soup.

7. George McGovern’s allegation that Richard Nixon tapes songs off the radio.

6. Rumors suggesting Abraham Lincoln’s hat concealed a “stovepipe head.”

5. Democrats’ claim Eisenhower wanted slogan “I lick Ike.”

4. Walter Mondale tearfully acknowledging his hazelnut allergy.

3. Suggestion that Barack Obama has surgically enhanced ears.

2. Mitt Romney’s investment in companies that order Chinese take-out.

1. Donald Trump offering $5 million to unearth anyone who still takes him seriously.