10 Harry Potter Moments You Never Knew Were Improvised

Mark Williams' portrayal of Arthur Weasley in the Potter saga may not have stolen the show, but his performance captured the part perfectly, providing a quirky, oddball secondary character that we truly believe is co-head of the Weasley tribe.

One of his most famous, popular and character-defining scenes comes in the first act of Chamber Of Secrets, in which he meets Harry Potter, discovers his sons have flown his enchanted Ford Anglia to Surrey and back, and enquires about his favourite interest: muggle artefacts.

Despite its apparent genius and hilarity, Arthur asking Harry 'What, exactly, is the function of a rubber duck?' is not a line from the film's script.

As Chris Rankin (Percy) revealed, Williams ad libbed a whole host of one-liners on the spot, and delivered a fresh one in each new take (which extended into double digits) to see which garnered the most laughs. Thus, the editors took their pick and a legendary quote was born - one that will outlive many of the speeches, exchanges and soliloquies the writers slaved over for days on end.

But, to the point at hand, what is the function of a rubber duck?