What is a terrorist's favorite song?
"Pumped Up Kicks."
What is a terrorist's favorite song?
"Pumped Up Kicks."
Okay, so basically, the joke is banking on the dark humor that terrorists, who are bad people that like to, uh, do bad things, would like the song "Pumped Up Kicks" by Foster the People because it's about a school shooting. Get it? It's funny because it's terrible. Also, you are not smart.