I'm at the Grand Galloping Gala is a song sung by Pinkie Pie during The Best Night Ever. She sings this to express her excited reaction to seeing the main hall where the Gala is taking place. The song is an altered version of the popular birthday song, "For He's A Jolly Good Fellow". This song's instrumental part was added by William Anderson after Shannon Chan-Kent recorded her vocals.
This song is BMI Work #13382133, which also gives credit to Daniel Ingram.