This is how The Symbiote follows Twilight goes in My Little Pony: Equestria Girls: The Symbiote Siren.
[Twilight starts up the portal to the Equestria Girls universe]
Twilight Sparkle: ...And the interval between the two points is defined as the square root of the sum of the squares of the separation between the points along three spatial dimensions.
Spike: Say what now?
Pinkie Pie: Duh! She's gonna take the magic in here and put it in there. That'll make the portal open up so that whenever she wants to, she can go from here to there. There to here. Here to there. Here there! Here there! Here—
Applejack: We get the idea!
Twilight Sparkle: Now to see if it actually works.
[The portal starts to open]
Main cast: Ooooh...
[It opens as the Equines look on in awe]
Main cast: Ahhhhh...
Applejack: Don't suppose we could join you this time around?
Twilight Sparkle: Better not. It could make things pretty confusing if Canterlot High all of a sudden had two of all of you.
Rest of main cast: [agreeing]
Spike: But I still get to go, right? There isn't another one of me at Canterlot High. And you never know if you might need your trusty assistant.
Twilight Sparkle: Mm-hmm.
Twilight Sparkle: We won't be gone long.
Fluttershy: Oh, you be careful, Twilight.
Rainbow Dash: Take care!
Applejack: Y'all be safe now.
Rarity: And don't forget to dress well.
Pinkie Pie: [squee]
Twilight Sparkle: Ready, Spike?
Spike: [sharpens his claw] Ready!
[Twilight and Spike charge into the portal but no one notices the Symbiote following]