Kim, 31, and Kanye, 34, indulged their inner kids on April 5, stopping by famous toy store FAO Schwarz to duet on the store's big piano -- just like the famous scene from Tom Hanks' classic Big.
"Kim took off her high heels and played the giant piano with Kanye," an onlooker tells Life & Style. "An employee taught them how to play 'Chopsticks' and 'Heart and Soul.'
"Kanye had the biggest grin on his face while bouncing back and forth playing 'Heart and Soul,' while Kim tried to keep up!"
The pair also wandered around the store together.
"At one point, they browsed children's books together and took delight in watching the demonstration of a magic trick," the onlooker adds. "They kept smiling at each other.... Kim ended up purchasing a blue Uglydoll [a doll that celebrates the beauty of a person inside and out]."
They created quite a buzz as they walked around the store together, even catching the attention of Caroline Kennedy, the daughter of JFK and Jackie O.
"She happened to be shopping at the store at the same time," the onlooker tells Life & Style. "Caroline was so curious about Kim and Kanye that she took multiple shots of the duo with her camera phone! She even craned it over heads to get a clearer shot. She went unnoticed [by the duo]."
Following their toy store outing, Kim and Kanye continued their day with dinner
"They sat in a private room," an eyewitness tells Life & Style. "They both munched on Fried Chicken N' Waffles and shared a Mac Attack, which is a tasting of three of the restaurant's macaroni and cheese dishes."
As Life & Style previously reported, Kim and Kanye were very touchy-feely while watching The Hunger Games at the Regal Cinema in Union Square on April 4. One day later, Kanye admitted to loving with Kim on his new song, "Theraflu."
"Kanye and I have been friends for years," Kim said coyly on Today this morning. "You never know what the future holds."