Note: The infamous Triple-dog-dare is infamous for the sole reason that you cannot back down from it--without exception! An issued triple-dog-dare has no counteraction and must be implemented and/or carried out.
Ever seen the movie "A Christmas Carol"? Enough said.
It is the ultimate dare. It's for when a person rejects a regular dare, AND a double dog dare. It is a dare that you HAVE to do under any circumstances. If you don't do it you look like a weakling or a chicken.
I triple dog dared her to run around the house completely naked. She chickened out and to this day we don't let her live it down.