you caught me in my nightie
When someone is caught in the act of wearing something that looks hideous. Usually clothes you wear at night. It doesn’t have to be a nightie.
Howard: oh no what are you doing here?
Martin: I’m just getting some milk.
Howard: oh no, you caught me in my nightie.
Martin: I’m just getting some milk.
Howard: oh no, you caught me in my nightie.