If you’re looking for something less practical and more for a practical joker, there is the inspired talking toilet roll dispenser. You can record your own message or jingle, which will play whenever someone takes any loo roll.
(A word of caution – some time ago my friends had a musical toilet roll holder. While undisputedly high on amusement and originality, their downstairs neighbours did complain about the noise. True story.)
For the more altruistic dad, there’s no need to have read all this – just twin your dad’s loo and tick Father’s Day off your to do list.
So go on, show your dads how much you love them!