Little of Archimedes's past is known. At some point, he became the pet owl of Merlin and gained the ability to speak. Like his owner, he has also had dealings with Madam Mim in the past, as he evidently fears her.
Archimedes is known for being somewhat grouchy and sarcastic, especially in the morning. Though he is loyal to Merlin, he is not afraid to point out the Wizard's shortcomings and often does. He is, however, very well educated, and possesses a great deal of practical knowledge.
Archimedes is based on Merlin's talking owl, from the book The Sword in the Stone, which the film was based on. Like the movie, the book version of Archimedes can talk and teaches Wart to fly.
Archimedes first appears with Merlin in their forest cottage. He scoffs at Merlin's idea that someone will join them for tea. Later, when a young boy named Wart does appear, he snidely reminds Merlin about his limits, when Merlin states that he can see everything in the future, as Merlin had no clue who the person was that would be joining them.
Archimedes accompanies Merlin as they travel to Sir Ector's castle, where Wart lives. Merlin introduces Archimedes as a "highly educated owl," which sends Sir Ector into hysterics, much to the offense of Archimedes. The next day, Archimedes protests that Merlin should return to the woods, as Sir Ector has placed the two of them in a crumbling tower, referred to as the "guest room." It rains that night, and Archimedes is soaked due to the numerous leaks in the tower. After Merlin sees Sir Pellinore come with news, Archimedes is sent to investigate. In the dining room, Archimedes overhears the men speak of an upcoming tournament, where the winner would become king of England.
The next morning, Archimedes is forced to remind a forgetful Merlin of where they are. The two then watch as Wart helps Kay practice his jousting. When Merlin scoffs at the idea that jousting is a science, Archimedes points out that Wart likes the sport just as much as the rest do. Merlin then reveals his plan to use magic to help Wart learn the value of an education.
Archimedes later accompanies Merlin as the wizard gives Wart a lesson. Merlin forgets the spell he intended to cast, and awakens a sleeping Archimedes for the spell. Archimedes is shown to be very cranky early in the morning and finds a nice tree to sleep in, while Merlin and Wart swim through the moat as fish. Archimedes suddenly woke up from the scream, as he is soon saw Wart being chased by a giant pike and quickly flew to the rescue. After Wart and Merlin are human again, Merlin slyly notes that Archimedes cared a lot about Wart's safety. This leads Archimedes to excuse himself on the basis that young perch is his favorite dish, and that he intended to eat Wart.
Later, when Merlin and Wart have transformed themselves into squirrels for another lesson, Wart is being chased by a lovestruck female squirrel. Archimedes' sleep is once again disturbed by Wart landing on top of him, to which the owl shoos Wart away, not knowing who he is.
Archimedes is next seen after Wart is fired as Kay's squire. Merlin begins Wart's education in earnest by talking about very complicated theories. Archimedes sees that Wart is getting confused and forcibly takes over Wart's education. Archimedes is shown to be much more practical than Merlin. He first tasks Wart with reading a mountain of books, but when he discovers that Wart can't read or write, Archimedes teaches him. During a break, Merlin demonstrates a model airplane. Archimedes believes that it won't work, and becomes hysterical when the plane crashes, due to it being caught in Merlin's beard.
When Merlin turns Wart into a sparrow, so that Wart can fly as he dreamed, Merlin begins to explain the concept of flight using Archimedes's wings as a model. Archimedes quickly stops this and decides to teach Wart to fly himself, as he himself is a bird. He teaches Wart to fly by making him do it. Everything is going well when a hawk appears and tries to eat Wart. Archimedes attempts to delay the hawk, and Wart is able to dive into a chimney to escape. When Archimedes sees that Wart is now in the hands of Madam Mim, Archimedes flies off to warn Merlin. Archimedes next appears as the Wizard's Duel is about to start, and he explains the premise to Wart. Alongside Wart, he watches the duel and occasionally yells out advice to Merlin.
At Christmas, Wart is made Kay's squire, to which Archimedes kindly congratulates him, but Merlin is furious with Wart's decision and goes to Bermuda. When Wart asks Archimedes if Merlin ever comes back, the owl only answers, "Who knows? Who knows anything?" Archimedes stays with Wart, accompanying him to London to the tournament. He goes with Wart as he attempts to find a sword for Kay. When Wart attempts to retrieve Excalibur, Archimedes warns him against pulling it. Later, he witnesses Wart being officially recognized as the rightful king Arthur and shows a mixture of happiness and disbelief.
After the coronation, Arthur feels unprepared for the duties of a king. Archimedes tries to help him run away, but they are unsuccessful as the castle is surrounded by cheering subjects. Merlin magically reappears to guide Arthur again, and Archimedes presumably chose to stay with them.