February 12, 1931 was the release date for Tod Browning's Dracula. As everyone knows, it was based on the 1897 Bram Stoker novel of the same name (or, perhaps more accurately, based on the Hamilton Deane stage play that was based on the novel), and featured Bela Lugosi in the immortal lead and Dwight Frye as Renfield. The Spanish-speaking version was released the same year, and was shot concurrently with this version, with a completely different cast and crew using the same sets when the original crew had gone home for the night. Although almost universally considered a classic, and with good reason, there are still plenty of faults to be found here, including some languid pacing and static, stationary camerawork. The latter has often been blamed on the difficult transition from the stage to the camera, but that's a cop-out answer. Motion pictures had been around for decades at this point, and Browning was no stranger to the medium, even if he was still warming to the notion of the talkie. Truthfully, a younger modern audience may have difficulty getting through this one.

Upon its initial run, Ingagi purported to be a genuine documentary, but it was discovered to be a hoax a short time later, setting the stage for the many mockumentary and "found footage" films to come, including Cannibal Holocaust, The Blair Witch Project, and Paranormal Activity. Ingagi was followed a decade later by Son of Ingagi, an in-name-only sequel.
Fritz Lang's classic M (his first talkie) hit German screens on May 11, 1931 and arrived in the United States nearly two years later. Scripted by the director in conjunction with Thea von Harbou (previously of Metropolis), this film starred Peter Lorre as the child-killer who is being hunted by both the police and the mob. All of the murders are implied, rather than shown, but the end result is still disturbing and jarring. Some have claimed that M is the last breath of German Expressionism, and the first breath of both the Film Noir and the Psychological Thriller. It is also notable for being one of the earliest films to utilize a leitmotif--a trick cribbed from the opera in which a specific character is identified with his own musical cue--which has become common place in modern cinema.
The Archie Mayo-directed Svengali was released on May 22, 1931, written by J. Grubb Alexander and based on the novel Trilby by George L. Du Maurier. It is a strange plot, to be sure: Svengali (John Barrymore) is a music maestro and a skilled hypnotist, who falls in love with the beautiful Trilby (Marian Marsh). He mesmerizes her, convinces her to fake her own death, and turns her into a beautiful singer. Under her new moniker of Madame Svengali, the two tour Europe together, garnering great fame until Trilby's former lover Billee (Bramwell Fletcher) comes looking for her. [Previously adapted as 1896's Trilby and Little Billee, 1898's Ella Lola, a la Trilby, 1914's Trilby, 1915's Trilby, 1922's Tense Moments with Great Authors, 1923's Trilby, and 1927's Svengali]
Only ten months after releasing Dracula, Universal Studios made history again with the November 21, 1931 release of James Whale's adaptation of Frankenstein. This film brought us Boris Karloff in his most famous role as the creature, Dwight Frye as Fritz, and Colin Clive as Henry Frankenstein. Not only does this movie give us the now-standard look of the creature created by makeup man Jack P. Pierce (which is copyrighted by Universal), but it also gives us the accepted methodology of creation: lightning. The method in which the creature was given life was never outlined in the novel, but it has nevertheless become an actual part of the mythology. Karloff would reprise the role in 1935's Bride of Frankenstein and 1939's Son of Frankenstein.
After a short break between adaptations, a new version of Dr. Jekyll and Mr. Hyde was released on December 31, 1931. This time around, it was directed by Rouben Mamoulian, written by Percy Heath and Samuel Hoffenstein, and starred Fredric March in the lead. Here, Hyde is depicted as a hard drinking, misogynistic skirt-chaser, and there was such overt sexuality on display here that when re-released in 1936, the then-fairly new Production Code forced the studio to remove eight minutes of footage. Luckily, those eight minutes were salvaged and restored for the home video market.