So there was this girl in my class. Who was on the large size. We'll call her Chip.
Anyway, one day this other girl, who we'll call Flea, had gone out of the classroom for some reason. So had Chip, for another reason.
Flea comes back, and quietly shuts the door behind her.
While she's standing in the doorway quietly shutting the door, unbeknownst to Flea but beknownst to everyone else in the classroom, Chip comes up behind her. Flea continues shutting the door, essentially in Chip's face, but not on purpose because her back is to the door.
"Oops, sorry Chip, I didn't see you there."
The class cracks up because, duh, Chip is large and we are teenagers, so this is hilarious.
The end. I have no idea why I remembered this today, or why this is such a strong memory, but there you go.