I'll confess, I'm a user and abuser of "That's what she said" jokes. I haven't watched "The Office" in a while, but the joke has stuck, latched onto by that little Tourretic component in my brain that thrives on such silly impropriety. I have a background process (a "daemon" as we say in geek-speek) that scans all incoming sentences for "Twss"-viability.* So...
I was in yoga class. Our teacher was explaining how to set up for a pose.** "...You might only need two blankets, but go ahead and add a third to the stack, because once you're in the pose, it's a whole lot easier to pull it out than it is to stick it in...." The dim meditative light hid my big goofy grin. But then from the back row, another student with an apparently similar juvenile sensibility (and a less effective verbal editor) whispered, almost inaudibly, "That's what she said," and I lost it, falling into a snorty giggling fit, as did the whisperer. The rest of the class (all higher-minded individuals, apparently) turned to stare at us. The teacher, puzzled, asked what was so funny. For a moment, I actually started to explain, "Um, well, you see, you said...", then realized I should quit while I wasn't too far behind. "Yeah, never mind..." Yeah. Really. Never mind. I'll grow up one of these days.
* And I define "viability" broadly. I love a good "That's what she said" zinger but also take a weird pleasure in applying it where it doesn't really apply (that's what she said), watching the joke land with an awkward plunk as everyone furrows their brows, thinking "That doesn't..."
** I do Iyengar Yoga. We use lot's of props in our poses, folded blankets and wood blocks and the like.