A person who is unable to successfully move their limbs due to extreme tiredness.
Conversing with said person is useless due to floppy donkey also affecting the brain.
To move someone who is a floppy donkey is close to impossible.
Guy "Honey do you wanna go somewhere?"
Girl *inaudible mumbling*
Guy "You're floppy donkey aren't you?"
I hate when she goes all floppy donkey on me, it's like she's made entirely of limbs!