Actually blackace, showing a boarding card stub IS compulsory so you should always have them readily available when boarding.
And I would say that was rather petty getting your own back on the crew member by making them walk around the aisle to speak to you. I would have been rather annoyed if I was that crew member, especially as from the information provided YOU chose to go down the alternative aisle forcing YOURSELF and your family to have to clamber over the pax is seat G
