Back in 2004, while filming Harry Potter and the Prisoner of Azkaban, Alan Rickman (with the help of Michael Gambon (Dumbledore)) hid a remote controlled fart machine inside a sleeping bag in a scene where Daniel Radcliffe was “sleeping” next to a girl he fancied. Hilarity ensued.
From an AMA Daniel Radcliffe did on reddit.com back in 2014:
From now on, Harry Potter and the Prisoner of Azkaban shall be known as Harry Potter and the Farts of Azkaban.
[Source: ShenronAlt on Youtube | Via Buzzfeed]