The best way to keep a secret from a F/A? Make a PA announcement.
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There was this pilot who hates taking check rides so has a mad scientist make a clone of him. The clone is perfect in every way, it looks like him, sounds like him and it flies like he does, the only flaw is that every other word out of his mouth is an obscenity. The pilot has a check ride the next day so he decides to send the clone in his place even with the clone's language problem.

The ride is going well and the clone is keeping up to ATP standards but every other word out of his mouth is a horrible, foul obscenity. After a while the check airmen can't stand it anymore so he opens a flight deck window and tosses the clone out and the clone falls to it's death.

When the check airmen lands he was arrested....He was charged with making an obscene clone fall.