How is “the joke's on” used?

In Meet John Doe (1941), one line is: “I'm afraid the joke's on us, let's go.”

Which movie is “the joke's on” from?

The clip at the top of this page is from Meet John Doe (1941).

I'm afraid the joke's on us, let's go.

8 作品で登場 · 1 本目

used to say that sb who tried to make another person look ridiculous now looks ridiculous instead

くだけた · 7 本の映画に登場

オックスフォード映画の 100%
used to say that sb who tried to make another person look ridiculous now looks ridiculous instead
I'm afraid the joke's on us, let's go.

定義：Oxford Advanced Learner's Dictionary 第 9 版