A childhood belief about tv

When I was little my mother used to watch Star Trek and as this was before I realised that most TV wasn't live. In one scene a character was wearing an outfit and then seconds later the scene changed to one later that day and there he was in another. I remember asking in bafflement how could actors change their clothes so quickly and my mother answered absently that they probably had a machine for it. For *ages* I believed that all actors had to run of stage and stand still while this little robot dressed them and then run off to act again. I asked my mother about this later and she said that because we'd been watching Star Trek she's thought I meant the characters getting changed rather than the actors.