Born March 25th, 1920, Patrick Troughton was the Second Doctor on the acclaimed tv series, and the first actor to replace the original Doctor, William Hartnell, and is thus the first regeneration of the Time Lord. It was a bold move on the part of the production team to replace the actor in the title role, and Doctor Who could have been a disaster from that point on. But it wasn't, and Patrick Troughton was the reason. His Doctor was unofficially known later on as "the cosmic hobo" due to the mannerisms that Troughton imbued the character with, but he could be as serious as needed when called upon. And when Troughton's Doctor was being serious, you knew that serious trouble was afoot.
Patrick Troughton's Doctor was my favourite in the role, though I also loved the William Hartnell Doctor. Sadly, much of Troughton's serials from the series no longer exist, and he is the most under-represented of the incarnations of the Time Lord on DVD.
So raise a glass today for the Second Doctor and the man who portrayed him so brilliantly, Patrick Troughton.