Teacher: Jeff, why did you throw a paper plane at the twins?
Jeff: You wouldn't get it, miss.
Teacher: Jeff, why did you throw a paper plane at the twins?
Jeff: You wouldn't get it, miss.
Alright, listen up, buttercup. The joke is dark because it references the Twin Towers, which were destroyed in a terrorist attack. Jeff's response implies that the reason he threw the paper plane at the "twins" is related to the 9/11 attack, but he knows the teacher is too dumb to get the reference. You probably didn't get it either, did you?