It's used in the twenty one pilots fandom and stands for the Few, the Proud and the Emotional. FPE is mentioned in the song Fairly Local (from Blurryface):
"Yo, this song will never be on the radio
Even if my clique were to pick and the people were to vote
It’s the few, the proud, and the emotional
Yo, you, bulletproof in black like a funeral
The world around us is burning but we’re so cold
It’s the few, the proud, and the emotional"
"Yo, this song will never be on the radio
Even if my clique were to pick and the people were to vote
It’s the few, the proud, and the emotional
Yo, you, bulletproof in black like a funeral
The world around us is burning but we’re so cold
It’s the few, the proud, and the emotional"
by aturtlenamedjosh January 03, 2017