I pretty much always love these threads. Basically the purpose is to post some sort of lyrics or melody that you can connect with the show's characters somehow.
In my mind, I like to picture music that could act as sort of the score for an episode, so my choices are mostly instrumentals from movies, games, classical music, etc.
Twilight - "The Sorcerer's Apprentice"
AJ - "In the Shade of the Old Apple Tree"
Rarity - "Eye Contact - Artist" from Pokemon Diamond/Pearl
Trixie - Theme from The Mask
Flimflam Bros. - "Powerhouse"
Luna - Theme from The Addams Family '91
Nightmare Moon - "Lost World Anthem" from Donkey Kong Country 2
Chrysalis - "The Silurians" from Doctor Who
Sombra - "Frozen Dinner" from Star Trek '09