President Trump and New York City Mayor-elect Zohran Mamdani looked more like long-lost best friends than political rivals during their first meeting at the White House on Friday — and according to a body language expert, Mamdani’s posture screamed one thing: he wanted to be a “good little boy” for Trump.

After months of trading insults, the two appeared surprisingly cheerful as they addressed reporters. Carole Lieberman, M.D., a body and brain analyst, told The Post that the whole interaction looked almost cartoonishly friendly.

“It seems as though someone may have diffused laughing gas into the meeting they just had, because both President Trump and Mayor Mamdani seemed almost giddy,” Lieberman said. “Their behavior towards one another was like a ‘love fest.’”

Lieberman said Mamdani’s posture gave away the dynamic. “Mamdani stood like a little school boy, his hands clasped together most of the time, trying his hardest to look like a ‘good little boy.’”

During the 30-minute press conference, the 34-year-old mayor-elect smiled nonstop, standing stiffly with his hands clasped in front of him. Trump, meanwhile, sat casually at the Resolute Desk like a man completely at ease — and completely in charge.

“Trump was very ‘hands on,’ tapping Mamdani and shaking hands with him,” Lieberman noted. “But he made sure he tapped Mamdani’s hand last, to indicate that Trump is the one in control.”

The pair said their private meeting focused on affordability and was “cordial” and “productive.”

“I met with a man who’s a very rational person. I met with a man who wants to see — really wants to see — New York be great again,” Trump said. “I’ll be cheering for him.”

Mamdani struck his own polite tone: “I enjoyed our conversation and I look forward to working together to deliver that affordability for New Yorkers.”

That level of friendliness is quite the shift. Mamdani previously labeled Trump a “despot,” and Trump famously called the socialist mayor-elect a “100% Communist Lunatic.”

Now, after one meeting, Mamdani looks like he’s auditioning to be teacher’s pet.