How I Met Your Mother: 10 Biggest Unanswered Questions
3. Who Is The Mother Of Barney's Daughter?
On a happier note, one of the best moments in the show's finale came with the revelation that Barney - after completing a "Perfect Month" - was going to become a father. During his final moments in the show, he casts aside his womanising ways and settles down to life as a parent.
Despite the twist's sweetness and a (mostly) great ending for the show's resident playboy, the mother of his daughter Ellie is never seen or even named, annoyingly referred to as "Number 31" every time she's even briefly mentioned.
There are plenty of ways the writers could have tried to tie up this loose end, maybe by bringing in a an ex like Quinn to fill the void and round everything out nicely, but tragically we're left to wonder who Barney had a child with until the end of time.