narcoleptic blink

An expression used when you say goodbye and mean to leave permanently but end up coming back immediately because you forgotten something. It jokingly means that the person you said goodbye to had a "narcoleptic blink" and fell asleep, and that you're not back already, but that you're back after doing whatever you were supposed to be doing.

-Ok, I'll see you later!
-Wait, why are you back already?
-Narcoleptic blink! Forgot my keys!