The other day a man kept tapping on the glass trying to mime a question to my colleague. She mouthed to him that she couldn't hear him through the glass and went back to her work. The man then stuck his finger in his mouth and drew a question mark on the glass in spit. (This same man later cornered my colleague outside on her lunch break and I had to rescue her).
On Sunday another man kept tapping on the glass in front of me. I finally looked up and he pointed frantically at the background picture to the "laboratory tools" exhibit to ask if one of the women in the picture was me. This would have been a sensible question, except that it's painfully obvious that this picture was made in the early 70's (e.g. half of the people in it have beehives, the other half cat-eyed glasses, the photo is in black and white, etc.) and the woman in it is at least 20. I mouthed that "No, that was way before I was born," which he just wouldn't take for an answer. Dude, I'm 22. I was not 20 in 1971, that's our lab manager who is in her 50s now. Accept it.