How is “be seeing things” used?

In Dave Chappelle: The Closer (2021), one line is: “I thought I was seeing things, I looked across the room and I saw...”

Which movie is “be seeing things” from?

The clip at the top of this page is from Dave Chappelle: The Closer (2021).

to imagine that you can see or hear sth that is in fact not there

informal · humorístico · Se oye en 8 películas

be seeing / hearing things
to imagine that you can see or hear sth that is in fact not there

Definiciones del Oxford Advanced Learner's Dictionary, 9.ª edición

I thought I was seeing things, I looked across the room and I saw...

En 8 películas · n.º 1