I like the implication that Twilight actually sang the entire song. Heck, she may have even sang all of them.
 
Come to think of it, why was Rebecca Shoichet credited in this episode? This is the only point in the episode where Twilight sings, but I find it very hard to believe they brought her in to sing one line as part of a development gag that doesn’t even involve her.

@Joshua
 
That makes sense.
 
I was gonna be all ‘Who hasn’t read this character in their voice when reading comics or stories?’

This little joke right here is actually a development parody; Tara Strong was originally going to voice both Twilight Sparkle and Pinkie Pie, but Andrea Libman was chosen to play the latter. That, and the voice would’ve hurt Tara’s throat due to the sheer high-pitched excitement in Pinkie’s voice.

Headcanon: Twilight often mimics Pinkie because she secretly admires her personality.

The season of imitation continues.