Secret Password

I was discussing with my sister the other day that we should find a "secret password" to tell people and let them know you know in case they know

Like the homosexuals who have their own secret password (I don't know if it is the same in english) "do you understand?"

So far the only one we could come up with was "I have no TV", which works wonders with both knowers and not-knowers alike.

I would welcome any suggestions