Re: How I Met Your Mother - season 4
Nick's right. It would be an awful cheat. But it would also be
impossible given the entire structure of the show and everything we've seen so far.
Ted is telling the story to his own kids who presumably have already
met their mother and know exactly who she is.

They also know who Aunts Robin is (as well Aunt Lily, Uncle Marshall and Awesome Uncle Barney.) None of this is a mystery to
them. He's just telling them the story of his pre-married life with these friends before he met the woman he would marry and who would bear his children. Why is this so hard for people to (a) understand and/or (b) accept?
This is one of those "journey is more important than the destination" situations. For
us who the mother ultimately turns out to be is an open question. But we're not Ted's audience. His kids are. For them the mystery is how the two of them ever got together - and
that is the story he's telling and we're eavesdropping on.
There is no way to follow the story and continuity that with any scenario in which Robin turns out to be the mother unless the show turns into an SF series in the final season and there's cloning and/or time travel involved.

Regards,
Joe