There's several cases of such delusion.
2 seconds sound clip from the Invasion of the Body Snatchers (1956) movie soundboard.
You can hear this line at 00:23:22.612 in the Blu-ray version of the movie.
Quote context
[...]
- There's something strange going on in Santa Mira.
- Dr. Kauffman calls it an epidemic of mass hysteria.
- Becky's cousin's got it for one.
- She thinks that her uncle and her aunt aren't her uncle and her aunt.
- There's several cases of such delusion.
- Now this isn't you yet, but there is a structural likeness.
- It's fantastic, but there must be some reason why this thing is in your house.
- Would you be willing to sit up with your strange friend, and see what his next move is?
- If nothing happens by morning, call the police. If something happens call me, will you?
[...]