"Transformation" joke

A boy and his Father visiting from a third world country were at an American shopping mall. They were amazed by almost everything they saw, but especially by two shiny, silver walls that could move apart and back together again.

The boy asked his Father, "What is this Father?".

The Father responded, "Son I have never seen anything like this in my life, I don`t know what it is!".

While the boy and his Father were watching wide-eyed, an old lady in a wheelchair rolled up to the moving walls and pressed a button. The walls opened and the lady rolled between them into a small room. The walls closed and the boy and his father watched small circles of lights with numbers above the walls light up.

They continued to watch the circles light up in the reverse direction. The walls opened up again and a voluptuous 24 year old woman stepped out.

The Father said to his son, "Go get your Mother".