A British idiom, said the actress to the bishop is a one-line joke, or punchline, which changes whatever has been said before it into an innuendo (i.e., it makes the previous dialogue vulgar or lewd). It is seen as especially funny if the previous dialogue was innocent in character. A variation is as the actress said to the bishop. This variation was used on a popular British television show, The Office. When that show was adapted for American audiences the idiom was changed to that’s what she said. The connection between the two phrases is unclear however, whether they both developed independently or if one influenced the other (of course the British version has been around longer). The
The phrase can be seen as derogatory toward women since there is no masculine version.
As you can see by the ngram above, the phrase rose greatly in popularity in the 1960’s and again in the 1980’s. It dropped in the 1990’s and then gained again. This was around the same time it was used on The Office, and we may have that to thank for the phrase sticking around.
Since this phrase is informal and slightly vulgar in nature, it does not appear often in the types of publications we mine for examples. However, we did find one instance of the American version.
She alluded to it once or twice—“You’re thinking, ‘When’s she gonna . . . ?’ She’s not gonna”—but mostly she stuck to her jokes, about “Yellow Submarine” and the phrase “That’s what she said.” [The New Yorker]