These are, in no particular order:
1. When you're a temp and someone comes wheeling around the edge of your cubicle, desperate to tell the funny story of What Happened to Them Over Christmas, and half-way into the first rude revelation, they realize you're not Sara or Becky or Todd or whoever usually sits there.
2. When my stomach growls loudly enough to be heard externally in a job interview because I was too nervous to eat beforehand.
3. Yesterday I was answering the phones at a temp gig, and as I answered the phone I realized I couldn't remember where I was. I was frantically scouring the desk I was at for a piece of letterhead, a business card, anything, but there was nothing, and the person on the other end was waiting for me to identify the business he'd just called, but I couldn't, so I didn't say anything at all while I was scrabbling for a clue. Then I started laughing to myself which undoubtedly came across as heavy breathing to the person at the other end. By the time I'd managed to work out the company name by reading it backwards where it was printed on the glass door in front of me, it was too late, I was laughing too hard, so I just hung up. They never called back. We must have sat in near-silence together for at least 30 seconds. I wonder what he thought?
4. Myself, jogging and falling down at that same gap in the sidewalk near Toasty's house. It wouldn't be nearly as funny if it weren't for those ads on TV for Miss Congeniality where Sandra Bullock wipes out. OK, it was funny the first time I fell. The second time was Christmas morning, and I was pissed off enough to shout curses -- "Santa is dead, you little bastards!" among them.
5. Inadvertently scaring the crap out of my upstairs neighbor (and myself). She was carrying a bunch of Christmas presents to her car and came down to our admittedly creepy parking garage in the elevator. I had a bunch of crap to carry up to my apartment, so I was waiting for the elevator down in the garage. When the door opened, I was standing directly in front of it. It briefly rained Christmas presents. Nothing was broken, so no harm, no foul.
6. This is an oldie but a goodie. Back when I was in graduate school, I had a class taught by the head of the Graduate Dept. He was a guy in his late 50s, I'd guess, and built on the Hemingway scale: big white beard, plus-size belly, generous ego. It was "presentation week," and the Prof was sitting amongst the students as student teams gave their presentations. One day, he was sitting in the back row; my friend Liz was next to him, and I was on the other side of her. During the students' talk, the Prof folded his arms across his belly and fell asleep. Something startled him, and he woke with this outrageous snort, throwing his giant head up and back. His glasses, which had been resting on his forehead, flew off and landed on a shelf behind him. There was a moment of chaos while he looked for his glasses on the floor and tried to pretend he'd been paying attention the whole time. Meanwhile, Liz, who is next to him, is struggling heroically not to laugh. I'm blocked from his line of sight by her thankfully oversized hair, laughing myself sick. The problem was that she could block his vision, but not his ears. My lungs were the size of raisins, but I couldn't re-inflate them without being heard. I thought I was going to pass out before I managed to sip in enough air to live on.
7. Same graduate school Prof., same Liz. We walk into the grad office, and the Prof is there, in one of his more expansive moods. As we walk in, his spreads his arms wide in a fatherly gesture and says, "Liz! Angst! How are things?" And Liz replies, "Great! How are your things?" There is a long, awkward moment of silence while we all evaluate the question and determine whether or not she's just asked the head of graduate studies about the condition of his genitalia. Then we all turn abruptly and flee.
8. Teaching in the Czech Republic. A students confuses "nipples" and "nibbles" and, asked to give an example of a verb in present tense, says, "the squirrel nipples his nuts." No one else hears the mistake. I have to excuse myself long enough to laugh to the point of nausea.
9. Teaching in England. I have a class of 14 students from Taiwan. Though I know nothing of the culture, I think I'm safe to assume that belching is not considered embarrassing or impolite. We met after lunch, and I do not know what they served in the cafeteria that day, but best guess would be Cucumber Deluxe. It was like sitting in a lake full of bullfrogs. Their faces were alternately confused by my inability to stop laughing and stretched wide to allow for the next eruption.
While this is by no means a definitive list, I'll stop here for the moment and ask my commenters to include any occasions where they desperately wanted to laugh but couldn't. And we'll all try hard not to LOL because we're at work and NOT reading blogs.