LOL, they put chocolates even if you behaved like a good boy :)Yes, which is why you see frequent flyers perched over their seats groping around behind them before they sit. ;-)
There is another variant preferred by adolescent females: the used chewing gum deposited on the seat upright. Generally it sticks to the victim's back when they lean on it, then it tracks across the victim's back as they move back and forward, generating a delightful cats-cradle appearance.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1