Found this on Pinterest (like most of the other stuff here) though this one is directly in another user's words, so I am mentioning this. The other stuff I usually edit a bit (or a lot. Most of it ends up Pinterest ideas, thoroughly edited and rewritten by me, I do mention when I copy someone else's idea word for word or very nearly)
I was waiting for the elevator when I randomly said "alohomora" way too loud as the door opened.
A girl looked at me in confusion and was like "what?"
And a guy looked at me as he smiled and whispered, "muggles."
Made my [bleep] day!