The song is from season 9 episode 13 of MLP:FiM.
Reprise: https://youtu.be/TeJHRze4yls | ♫ Lyrics for the song:
( You can support the show here: https://itunes.apple.com/us/tv-season/my-little-pony-friendship-is-magic-season-9/id1458376743 )
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[Princess Celestia]
There's a lotta little things you gotta do in this world
[Princess Luna]
There's a lotta little things you gotta try
[Princess Celestia]
Just a pack of punchy plunges other ponies all take
[Princess Luna]
That have princess-pony-passed us right by
[Both]
Nopony knows you like your little sister
Nopony is a better confidante
Nopony is truer than the one you are
Nopony else here I could want
[Princess Celestia]
You can't saunter on a sojourn hid behind castle walls
[Princess Luna]
You can't throw a throne down on the beach
[Princess Celestia]
So we're gonna be absconding
[Princess Luna]
To a little vagabonding
[Princess Celestia]
And this bucket list is gonna be a peach
[Both]
Nopony knows you like your older sister
Nopony is a better confidante
Nopony is truer than the one you are
Nopony else here I could want
There's a lotta little things you gotta try in this world
There's a lotta little things you gotta see
[Princess Luna]
But just reading by a river and resting our hooves
Would practically be perfect for me
[Both]
Nopony knows you like your sister
Nopony is a better confidante
Nopony is truer than the one you are
Nopony else here I could want
[Princess Celestia]
You can't venture on adventures if you're taking a nap
You can't check things off your checklist while you sleep
So let's take another hill
[Princess Luna]
Sometimes you can be a pill
And why's the way ahead always so steep?
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"My Little Pony" is owned by Hasbro,
"MLP: Friendship is Magic" is created by Lauren Faust.