Amusing footage has emerged from Australia of a dad pranking his young son with "invisible horn buttons" in the front of a car.<br /><br />Self-styled "mad scientist" Jacob Strickling installed an extra horn inside a new car with a secret foot switch to operate the horn hands-free.<br /><br />In the clip, Jacob picks up his son Samuel, 8, and convinces him that the new car has secret buttons.<br /><br />Every time Samuel presses something in the car, dad secretly operates the horn with his foot switch. <br /><br />Samuel finds it hilarious but eventually big sister Mikalah works out what's going on and gives the game away.<br /><br />The clip was filmed on April 20 in Gosford, New South Wales.
