I've been trying to find this commercial online because you have to hear it to know how irritating it is. It's the video inside the link.
https://www.ispot.tv/ad/6M_r/no7-lab...-action-secret
The woman spouts a 50 year old joke followed a microsecond later by "Kidding!" just in case people actually thought she was going to kill the other woman.
Who thought this was a good idea? I have to think that it was a 23 year-old female advertising junior copywriter who had only recently heard the joke, but she was concerned that most people had never heard it and would take it seriously. And it's not just terrible in general, but it's terrible in context. She tried to use this line on women comparing makeup. It makes no sense at all.