Used to describe the experience of spontaneously falling asleep, usually in a potentially sexual situation with an ex-boyfriend. Narcoleptatastic can also be used as a way to describe sleep faked in order to avoid the same type of situation. It is also used to describe having fallen asleep without realising, though to a much lesser extent.
"That night with *ex-boyfriend's name* was narcoleptatastic!"
"One minute we were talking about shrimp, and the next I was waking up. It was narcoleptatastic."