Laughter is infectious. Sort of like whistling. You can whistle a little tune somewhere with a bunch of people (grocery store, mall, whatever) and soon someone else will start whistling. Try it. You'll see.
There's also some kind of syndrome where people laugh or cry uncontrollably.
I had an embarrassing incident like that many years ago where the management of the company got us all together to demonstrate a new giant pen-type printer for the drafting department for size "X" (or whatever) drawings... about three feet wide.
The demo software had the thing drawing a huge pattern of circles and radial lines, and it would make squeaky noises as the pens drew the pattern.
It struck me so funny because the noises reminded me of a squeaky bed with a couple engaged in intercourse on it.
Right down to the speedups and slowdowns as their passions waxed and waned and approached climax and slowed down to enjoy that moment more. And it would stop for a second while the machine dropped off and picked up another colored pen.
I could imagine "them" taking a few seconds to catch their breath, then starting up again as the printer started drawing in a different color, faster and faster and faster.
Finally it approached the middle of the drawing where there were a lot of shorter and shorter pen-strokes going faster and faster as the lines got shorter and shorter and I completely lost it.
It then slowed down to draw the borders of the drawing, as if my imaginary couple-on-the-bed were engaged in that slowdown of final sensuality.
I actually fell on the floor from laughing so hard, and what made it worse --or funnier --was that nobody else was "getting" it the way I was.
Damned good thing "Bolero" wasn't playing somewhere in the background.
Or one of Strauss' finales.
To this day, I could swear the guy who created that demonstration pattern had those noises in mind in the first place.
Yeah, I gots me a sensa yuma that sometimes gets me in trouble.
Terry, 230RN