Me, making a joke: "See, I'm not ever going to get dementia, I just struggle with a persistant inability to finish my..."

Coworker: "Finish your what?"

Me: ::waits expectantly for her to get it::
Me: ::and waits::
Me: ::and waits::
Me about three minutes later: "You know, if I'm lucky, you're going to get that in the middle of the night and it will keep you up."

Coworker: "I don't understand what you said! You just said you couldn't finish your... and then never said anything!"