10 Harry Potter Moments You Never Knew Were Improvised

Yet another crucial character moment from Chamber Of Secrets improvised by Jason Isaacs comes in the very next sequence from his and Harry's back and forth in Dumbledore's office, beginning with Lucius kicking Dobby the house elf down the headmaster's stairs.

As Dobby is 100% CGI, director Chris Columbus assumed Isaacs had stumbled slightly while filming, but in fact he was envisioning a whole extra element to the scene, with the pureblood patriarch taking his anger out on his devoted and self-hating slave, Dobby.

But Isaacs didn't stop there, oh no. This doubles up with another improvised moment as Harry follows Lucius to the corridor outside the office's golden guardian statue. He proceeds to use the ol' sock-in-a-book ruse to free Dobby (presenting an elf with an item of clothing sets them free) and this sends Lucius over the edge.

Isaacs forgot the scripted spell and reached for the first thing in his mind, presumably from reading the books - the killing curse. In a fit of pure hatred and rage, having just lost his elf and his pride, he can be heard beginning the incantation Avada Kedavra, before being pinged across the room by Dobby, the newly-minted Free Elf.