If all those present were laid end to end, I wouldn’t be at all surprised.

The line is a risqué twist on a long-running joke format that imagines a large group being arranged “end to end” to make a point. The earliest close match in the provided material appears in a 1934 essay collection by Alexander Woollcott, where he reports it as something Parker said about a Yale prom.

It uses a mock-statistical setup to deliver an innuendo: instead of emphasizing the group’s size, the punchline implies a sexual scenario, with the speaker pretending that the resulting arrangement would be unsurprising.

If all the girls attending it were laid end to end, Mrs. Parker said, she wouldn’t be at all surprised.

If all the girls who attended the Yale Prom this year were laid end to end, I wouldn’t be a bit surprised.

If all those sweet young things present were laid end to end, I wouldn’t be at all surprised.

If all the girls were laid end to end, I wouldn’t be surprised.