A childhood belief about imaginary friends

My son had three imaginary friends at age three. One day at lunch, she held out his arm and wiggled his head. He said " look mama, a little elephant, then he did it again, and said " well, lookit there, it's a little mouse, and again, "I be darn, anoder little mouse, but he's grey.
The mice were with us for a few years, and went everywhere with us. Peter was the grey mouse, and he would fly outside the car we we drove, he'd even role down the window to let him in. Once he let his grandpa keep Peter in his pocket, while my son kept the brown mouse in his. Then when they had sit down to order, my son said, Where's Peter Pop? His grandfather answered, He's still in my pocket. Then my son, in his usually load voice said: "Well Papa, Why don't you take your Peter out of your pocket and put it on the table" His papa couldn't stop laughing, neither could the waitress.