Barack Obama and Donald Trump shared a conversation and smiles during the memorial service Thursday for President Jimmy Carter at the National Cathedral in Washington, D.C. ROBERTO SCHMIDT/AFP via Getty Images

Former President Barack Obama and President-elect Donald Trump appeared to be engaged in a deep, intimate discussion during the memorial service for President Jimmy Carter on Thursday at the National Cathedral.

Both men could be seen laughing as the two rivals chatted.

At one point, Obama nodded several times as Trump leaned in during the conversation.

Melania Trump, seated to Trump's left, stared straight ahead during their extended exchange.

Social media erupted in speculation about what the two presidents were talking about.

Donald Trump smiles as he and Barack Obama chat before the service Thursday for President Jimmy Carter at the National Cathedral in Washington, D.C. RICKY CARIOTI/POOL/AFP via Getty Images

"Think he's telling Obama about Greenland? Or the Gulf of America," posted The Great Gig in the Sky on X.

"Nah, talking about birth certificates," said another on X, referring to Trump's false claim that Obama wasn't eligible for the presidency because he was born in Kenya.

One suggested Melania Trump eavesdrop.

"Melania can you lean a bit to your right so we can get clearer audio of the conversation?" posted TayoMurph on X, linking to a photo of Russian leader Vladimir Putin.

The service for Carter, who died Dec. 29 at the age of 100, brought a rare gathering of five presidents together - Obama, Trump, Joe Biden, George W. Bush and Bill Clinton.

Sitting in the pew in front of Obama and Trump were Vice President Kamala Harris, who lost the 2024 presidential race to Trump, and her husband, Doug Emhoff.

Beside them sat Biden and first lady Jill Biden.

Bill and Hillary Clinton, and Bush and former first lady Laura Bush sat to Obama's right.

Former first lady Michelle Obama did not attend the service due to a scheduling conflict.

Carter's casket was transported from the U.S. Capitol to the National Cathedral on Thursday morning for the service.

He will be buried later Thursday at a private ceremony in his Plains, Ga., hometown next to his late wife, Rosalynn.