Curious cat on the street

One day I drove up to my house, and I saw my friend in the car window. She came up, we talked for a minute, I opened the car door, went out. We stand aside, it was a silence around, suddenly the car alarm started to give loud signals. We did not understand why. I came closer, everything was fine. I opened the door, and discovered one of the street cats was in my car. He imperceptibly slipped inside at that few seconds, when I went out from the car and was closing the door. It was so quickly, that nobody noticed. After half an hour I was planning to drive to Norway, and I imagined the situation if the cat would remain and slept quietly in the back seat, and how I would prove that I don’t have animal with me, when at the custom I would be pointed out on “my cat”.
I released the cat from the car, but when I returned, the same cat got off the roof and stayed in the car. He walked and then sat in the front until one of the cats called him with the loud “Meow”, the cat in front of me also answered “Meow”, and then ran to sharpen the claws on the nearby tree.