Donald Pleasence did not receive an Oscar nomination for portraying Dr. Samuel Loomis in Halloween.
Donald Pleasence actually is not in this film a great deal and I would not argue if someone placed him in supporting for this year. Pleasence though only leads his scenes as they are basically the only scenes without the ominous camera that seems to suggest the vision of the killer. Pleasence plays the doctor who try to treat Michael Myers in the mental institute and later becomes the one who sees that Myers needs to be locked up tight for the protection of everyone. After Myers escape, Pleasence is the hero of the film by being the man trying to track him down and stop him.
The casting of seasoned actors in horror films, with otherwise fairly unknowns in the cast, is quite a common occurrence. What is also a common occurrence though is that veteran actors makes quite known they are only doing for a paycheck and give a terrible performance like Richard Burton in the Exorcist 2 for example. Donald Pleasence though does not such thing bringing the utmost conviction with his performance that neither plays the role just to ham it up, or just to look visibly bored. Pleasence has a very important part in basically bringing the substance to the situation, and adding to the film's grim atmosphere.
Pleasence really brings a dramatic weight to every one of his scenes as Loomis tries his best to warn everyone about the threat that Michael Myers holds for everyone. Some of the lines he has honestly could have gone very wrong as some are rather extreme and quite close to being absurd as written. Pleasence though says every line he has with the utmost conviction and not only make them seem to be natural things that Loomis would say, but he also really gives them a genuine power through his performance. Pleasence finds the truth of every line and completely carries the screenplay as it might of faltered with a lesser actor.
One thing that Pleasence does extremely well here is create Dr. Loomis into his own character even though he really does not have any personal scenes to tell where Loomis has come from. Pleasence makes Loomis as clearly a nervous man who has been changed by his experience. Pleasence suggests this state through his physical performance where he has Loomis always seems a bit on edge although because of that he is the one man ready for the monster that is Michael Myers. Pleasence is incredible because without even showing any scenes in his past gives a portrait of a man who has been shaped through his time with a patient that has made it so he has seen evil incarnate.
A great scene for Donald Pleasence is when he tells his story quickly to a cop and how he came to know that Myers needs to be stopped at any cost. The pronounced yet subtle fear Pleasence is able to convey is remarkable. When Pleasence as Loomis describes the complete lack of morality that he saw in Michael Myers, Pleasence vividly creates the image of Myers for us. Pleasence creates just through his words the hollowness of Michael Myers and creates a greater depth to the monster then would otherwise be there. Pleasence, who barely even interacts with the monster, fleshes out Myers more as a character through his portrayal of the haunted Loomis.
Pleasence plays a most unorthodox hero in that Loomis is a step behind Myers until the end as well as that he does not interact with our heroine Laurie (Jamie Lee Curtis) until the very last scene. Pleasence though is exceptional in this role in portraying the intense yet very quiet drive in Loomis to try and stop Myers before he goes on a killing spree. Pleasence in an unassuming yet passionate fashion builds perfectly to the moment in which Loomis finally finds Michael and immediately takes action. The ending does not seem rushed in slightest because Pleasence in his scenes properly builds to the moment.
Pleasence delivers in each of his scenes building the atmosphere of the film brilliantly and bringing more to the part of Dr. Loomis then perhaps even the director John Carpenter expected him to. Pleasence serves all the needs of the story to bring substance to the horror story and realizes Loomis fully as a character who could easily have thrived as a character even beyond the strict confines of this film's story. His performance easily could have been the lead to a straight drama just about a doctor dealing with the criminally insane in down to earth fashion. This is just a terrific example of an old pro giving it his all and putting to shame actors who do not give even the slightest effort in this type of role.