"What if you found a portal to a parallel universe? What if you could slide into a thousand different worlds?" - Sliders
Twilight decides to return to the human world to document its existence. But there are multiple mirrors with different human worlds (all starred by Tara Strong's characters).
For the curious, the thing around Twilight's neck is a Blackbirdfly Twin Lens Reflex [link]
camera used by another character that ventures into parallel worlds.