Daniel Ingram is one sneaky musician! This was going to be in the episode followup, but I figured I'd split it off since so many of you are sending it.
Apparently a neat little inside joke was placed into the Cadance song. Kwulhu over on Reddit did what bronies do best: analyze the hell out of something. What he found was actually really neat! Have his quote:
There was actually a double meaning in the song. The song is in the key of Db Major (just like winter wrap up!) . That means that the root chord is a Db major chord. Usually, a Ab major chord will lead into a Db major. This is the V-I chord progression and it is also known as the Authentic Cadence (stick with me here). Now, it seems to resolve to a sadder chord at the end of the phrase. Instead of ending on Db major around 1:16, it lands on Bb minor: the relative minor of Db major. Now, when a chord progression seems to be heading to the root chord but lands on the relative minor instead, that is called a...Later on, Daniel actually confirms it.
Also worth noting, listen to how Twilight sings the last "forever" in the song. Her little cadenza (I am seriously not making these words up) quotes the opening notes of the theme song
I wonder what else he has snuck into our favorite pony tracks?