The two countries even did a joint rehearsal of their two leaders meeting, shaking hands, and walking around the grounds of the Demilitarised Zone using stand-ins to make sure every second was calibrated as best as possible for the world's cameras.
But for a moment on Friday, Kim went completely off script.
After shaking hands with Moon and stepping across the border line into South Korea, Kim invited Moon to step back into North Korea with him.
The South Korean president's residence, The Blue House, confirmed the moment was "unscheduled." According to a spokesman, Moon asked Kim, "When do I get to visit the North," to which Kim replied "Why don't you just come over to the North side now?"
The sudden invite didn't appear to worry Moon, who was seen laughing and talking with Kim, before the two paused for a handshake on the North Korean side.
At another point, Kim appeared to go off script again joking about the famous cold noodles he had brought in from Pyongyang, which is "far."
"I suppose I shouldn't say 'far' now," he seemed to quickly backtrack.
But the two moments, however light-hearted, will probably be taken very seriously by the American intelligence community.
Kim is an incredibly secretive leader — he even travels with his own toilet to prevent his health being analysed through his excrement — which means intelligence officials rely on any and all clues to understand how he thinks and operates.
Intelligence officials told Reuters that experts will closely watch the inter-Korean summit and analyse what Kim says as well as his body language.
The current profile of Kim focuses on his tendencies for ruthlessness as well as rationality. But inviting Moon on a surprise visit to the North could also hint at a tendency for spontaneity.
This could pose a problem for the Trump administration's strategy for meeting with Kim.
Trump himself is incredibly spontaneous, often veering off-script in ways that can create awkward, and at times, offensive, moments with world leaders.
Having two leaders with a propensity for improvisation steer the US-North Korea summit could create a positive middle ground and help build a personal relationship between Kim and Trump.
Or there could now be twice the chance of something being done or said in error, spelling disaster for bilateral negotiations.