The one that I'll probably remember forever was when I was still living with my parents, a brother and two sisters. I must have been in my late teens at the time.
We saw a couple of Mormon missionaries coming up the drive to state their positiion, and I got elected to get rid of them. My brother and two sisters were upstairs and the missionaries came to the front door which is immediately at the bottom of the stairs. My youngest sister, who is a great actress, started moaning as if she were in extremitis about two minutes into my futile attempt to get rid of the two Mormons. Very loud and painful, it sounded. Kate, the elder of my two sisters, came downstairs with tears in her eyes (from suppressing laughter) and whispered "Last rites!" in my ear. Then she went back upstairs "crying". My brother was making some interesting noises in the background as well, and I was having a hell of a job not to laugh myself.
I told the missionaries that my youngest sister was dying of something contagious and that the priest would be there any minute to administer the last rites.
I dunno if they believed me, but they took off like scalded cats ...
Bit difficult to do without some siblings willing to play along, I suppose.
