Example from my life:
Nurse [checking my empty IV bag]: "You sucked it dry"
Aside from occasional harmless chuckle (and a sense of pride at a well-placed joke of my own), I had not given "That's what she said" much thought. Maybe the writers of The Office created the phrase, maybe they didn't. The other morning while getting ready for work, Wayne's World (1992) was on television. I've seen it many times, but I guess this line went over my head in the past:
[Wayne and Garth discuss Claudia Schiffer.]Garth Algar: She's magically babe-a-licious.
Wayne: She tested very high on the stroke-ability scale.
Garth: Hey, are you done yet? I'm getting tired of holding this. (referring to Claudia's picture)
Wayne: Yeah, that's what she said.