I love their butts!

Scootaloo: Hey, what gives?  
Spike: A-ha! Twilight might thought you’d show your little faces around here, so she set up a force field!

Why couldn’t you do this when Tirek attacked Twilight…
 
;_;

@JP  
I think one of Twilight Sparkle’s hobbies is studying other unicorn’s spells and copying them. She copied Rarity’s “gem-finding” spell and Celestia’s “reveal hidden doors” spell, so it stands to reason she copied Shining Armor’s “force bubble” spell as well.
 
Recall that Twilight’s Mom appears to be the G1 Twilight, whose signature move was teleportation. Some day I hope to see an episode where we find that Twilight Sparkle learned teleportation by copying her mother.

I do not see the point of a snow globe this large

The outline shape of that shield bubble is actually quite wrong. Where it touches the ground should be an ellipse with the tree at the centre, but it looks more like the shield is centred around a point in front of the tree and doesn’t reach all the way around the back. The bottom ellipse needed to be much “deeper” to give proper perspective.

@JP  
I think Twilight learned it herself. Giant force fields are possibly one of the high-level magic abilities for unicorns and alicorns.  
Shining Armor probably learned the spell through requested training with Celestia.

@JP  
A little of Colum A and a little of Colum B.

I wonder, did Shiny teach Twi how to create force fields, or was it Twi who figured it out? Or are force fields common knowledge among unicorns?

When Twilight masturbates, she makes sure no pony bothers her.