Kirk Douglas is eternally fun to draw - from his his impossible chin to his constant steely intensity, seemingly on the verge of cracking every molar or shredding his throat with every line he delivers - Kirk Douglas was a pioneer, way ahead of his time in Hollywood.
Some of his films you need to see (if you already haven't already):
Ace in the Hole (Directed by the incomparable Billy Wilder), Spartacus (written by blacklisted writer Dalton Trumbo, who Douglas insisted on hiring and then very publicly stated that he had done so, quite effectively beginning the process of ending the blacklist for once and for all. Oh yeah and directed by Stanley Kubrick),
Lust For Life (effectively capturing Vincent Van Gogh's conflicted artistic and emotional turmoil unlike anyone before or since) Paths of Glory (Kubrick again - a searing indictment of the insanity and arrogance of the first World War), 20,000 Leagues Under the Sea (Disney does Jules Verne), Gunfight at the O.K. Corral (playing Doc Holliday to Burt Lancaster's Wyatt Earp, with none of that sappy "Huckleberry" nonsense), Town Without Pity, Lonely Are The Brave, The Bad and the Beautiful, the list goes on and on...
Watch any of these iconic performances and you'll see why Kirk Douglas is an icon, and also - all due respect - why Michael Douglas is good, but not Kirk good.
BTW - the reason Michael Douglas is one of the Producers of the film One Flew Under the Cuckoo's Nest is that Kirk Douglas held the rights for the film version of Ken Kesey's book. Kirk had hoped to one day play McMurphy on the big screen (and OMG what an amazing thing to behold that would have been! Read the description of McMurphy in the book and you will not picture Jack Nicholson, but you could totally see Kirk in the role, in his prime...) but by the time Hollywood was ready to fund and make the film Kirk was too old to play McMurphy, so he gave the project to Michael.