You know `em... those times your mouth (and other parts) get ahead of your grey matter.

Like saying, "That's not Brain Science (or "Rocket Surgery)".
A buddy once desribed an individual he knew as being "paralyzed from the waist up".
Or maybe you mixed up song lyrics and came up with some strange images, or perhaps a new verse, like:
(instead of I'll Tell Me Ma):

My Pa told Ma, when he got home
"Clean up the house; get off the phone!"...


You know ye got `em. Let's hear `em!

Testify, o ye brothers and sisters!