In the finale, I REALLY wanted to see pinkie pie be able to wield Discord’s magic. We did get to see that she was not corrupted by it. And I think, with training she would be a wonderful creature to inherit this power. This concept, (plus my belief that Twilight would be driven crazy by grief of outliving her friends and the weight of her responsibilities) inspired my rather odd headcanon of Twilight and Pinkie keeping each other company as immortals. The full explanation of this idea can be seen in the reddit link.  
(Though I am fully aware that I am not the first to play with the “Twilight sparkle is not cut out for immortality” concept)