As Twilight attempts to get Starlight Glimmer to see the error of her ways, Spike can't help but interject. If Starlight had a portal to take her to any place or any time, why fixate on one single event when she could accomplish so much more?
As it turns out, Starlight Glimmer has an answer. Several in fact.
Inspired by a conversation with the story's editor Tired Old Man.