The former N.B.A. star Dennis Rodman has always had an ability to grab the spotlight. There was the time he donned a wedding dress and claimed to marry himself. There were his stints on reality television and as a pro wrestler. And there was his unusual relationship with the North Korean leader, Kim Jong-un, to whom he sang “Happy Birthday” in 2014.

So when President Trump and Mr. Kim began their historic meeting in Singapore on Tuesday, it seemed inevitable that The Worm, as Mr. Rodman is known, would make an appearance.

The retired basketball star has met both men and forged unlikely ties to North Korea, traveling to the isolated authoritarian state several times and once taking a team of retired basketball players to Pyongyang, the North’s capital, to play before Mr. Kim.

In an emotional interview with CNN shortly after Mr. Trump and Mr. Kim shook hands, Mr. Rodman expressed his hopes for the meeting, declaring, “Today is a great day.”