everyone and their mother

代名詞

慣用表現

(idiomatic) A large number of people; most people.

日本語の意味

大勢の人々 / ほとんどの人々 / 非常に多くの人々

When the new cafe opened, everyone and their mother showed up for the free pastries.

新しいカフェがオープンしたとき、大勢の人が無料のペストリーのために押し寄せた。

意味（1）

(idiomatic) A large number of people; most people.

2011, "Now Everyone And Their Mother Is Shorting China, Especially These Four Stocks", Business Insider