Susan and the secret code

It was a sunny spring afternoon. Susan was sitting on the swing, and waiting for her mother to pick her up from school.
Suddenly she saw a man and waved to him. “Hi, Uncle Matt,” she said. «What are you doing here?” “Your mother asked me to pick you up from school today.
She’s doing some shopping for dinner.”
Susan smiled at her uncle. She and Uncle Matt always had such fun
when he came to visit. They played hide-and-seek, “Monopoly» and other games.
Susan said, “I’m ready to go, Uncle Matt, but I need to hear a secret code first. Mum said I can’t leave school with anyone if they can’t say the secret code.» Uncle Matt looked surprised, “A secret code? I don’t know any secret code. What is it?» Susan smiled, “I can’t tell you a secret code. You must tell me!» “Why,” said Uncle Matt, “don’t you know it?» “Of course I know it. The secret code is what only my parents and I know. When they can’t collect me from school they tell the code to the person who comes to pick me up. This person says the secret code to me and I know that it’s safe to go with them.”
Uncle Matt smiled. “Come on, Sue, I’m not a stranger. You know me. I think your mum just forgot to tell me the secret code.” Susan looked down and said in a small voice, “Mum said I can’t go with anyone if they can’t tell me the secret code.”
Susan looked up at Uncle Matt and said, “Uncle Matt, you must phone my mum and ask her for the secret code or I’ll have to ask my teacher what to do.”
«OK, Susan,” said Uncle Matt, “I know the secret code. I was testing you to see if you know what to do. Your mum worries that you don’t understand how important it is that you go only with people who know the secret code. You passed the test with flying colors!”
Uncle Matt smiled and said, “OK, Sue, now we can go home!» Susan shook her head and shouted, “But you haven’t told me the secret code, Uncle!”
Uncle Matt whispered in Sue’s ear, “The Pink Panther wears blue socks.» Susan smiled. “That’s right! Now I can go with you!» She waved goodbye to her classmates and set off for home with her uncle.
When they were walking home Uncle Matt said, “That’s quite a secret code you have!» Susan answered proudly,
“I made it up myself!»