20 Things You Didn't Know About Star Wars: Episode I - The Phantom Menace

11. Ian McDiarmid Didn't Know He Was Playing Palpatine Until He Arrived On Set

Ian McDiarmid of course plays the dual role of Senator Palpatine aka Darth Sidious in the Star Wars prequels, but given that his much-younger self played the grotty Emperor in Return of the Jedi, he initially assumed that Lucas would be casting a younger actor to play the character in the prequels.

Moreover, Lucas trolled McDiarmid by keeping him in the dark until just before the cameras started rolling - he told the actor he would be playing a Senator, and only found out about Palpatine when he reported to set.

McDiarmid, ever the professional, did a fine job pivoting and delivering arguably the most entertaining performance across the prequels. Still, blindsiding him with the precise nature of his role last minute sure was a gamble...