He acted in Mad Love (1935), Crime and Punishment (1935), The Maltese Falcon (1941), Casablanca (1942), Arsenic and Old Lace (1944), Passage to Marseille (1944), and My Favorite Brunette (1947).

[6][7] Lorre began acting on stage in Vienna aged 17, where he worked with Viennese Art Nouveau artist and puppeteer Richard Teschner.

The actor became much better known after director Fritz Lang cast him as child-killer Hans Beckert in M (1931), a film reputedly inspired by the Peter Kürten case.

[11] Sharon Packer observed that Lorre played the "loner, [and] schizotypal murderer" with "raspy voice, bulging eyes, and emotive acting (a holdover from the silent screen) [which] always make him memorable.

"[9] In 1932, Lorre appeared alongside Hans Albers in the science fiction film F.P.1 antwortet nicht about an artificial island in the mid-Atlantic.

In The Guardian, September 2014, Michael Newton wrote, "Lorre cannot help but steal each scene; he's a physically present actor, often, you feel, surrounded as he is by the pallid English, the only one in the room with a body.

"[14] Lorre and his first wife, actress Celia Lovsky, boarded the Cunard-White Star Liner RMS Majestic in Southampton on July 18, 1934, to sail for New York a day after shooting had been completed on The Man Who Knew Too Much, having gained visitor's visas to the United States.

[19] For MGM's Mad Love (1935), set in Paris and directed by Karl Freund, Lorre's head was shaved for the role of Dr. Gogol, a demented surgeon who replaces the wrecked hands of a concert pianist with those of an executed knife murderer.

[30] The second RKO film, also in 1940, was You'll Find Out, a musical comedy mystery vehicle for bandleader Kay Kyser in which Lorre spoofed his sinister image alongside horror stars Bela Lugosi and Boris Karloff.

[33][34] Although Warner Bros. was lukewarm, Huston was keen for him to play Joel Cairo, observing that Lorre "had that clear combination of braininess and real innocence, and sophistication...

"[34] Lorre himself reminisced fondly in 1962 about the "stock company" he now found himself working with: Humphrey Bogart, Sydney Greenstreet and Claude Rains.

Lorre made nine movies with Sydney Greenstreet counting The Maltese Falcon and Casablanca, a team which came to be called "Little Pete-Big Syd", although they did not always have much screen time in joint scenes.

[36] Most of these motion pictures were variations on Casablanca, including Background to Danger (1943, with George Raft); Passage to Marseille (1944), reuniting them with Humphrey Bogart and Claude Rains; The Mask of Dimitrios (1944); The Conspirators (1944, with Hedy Lamarr and Paul Henreid); Hollywood Canteen (1944); Three Strangers (1946), a suspense film about three people who are joint partners on a winning lottery ticket, with third-billed Lorre cast against type by director Jean Negulesco as the romantic lead, also starring Geraldine Fitzgerald; and Greenstreet and Lorre's final film together, suspense thriller The Verdict (1946), director Don Siegel's first feature, with Greenstreet and Lorre finally billed first and second, respectively.

Lorre returned to comedy with the role of Dr. Einstein in Frank Capra's version of Arsenic and Old Lace (released in 1944) starring Cary Grant and Raymond Massey.

Daniel Bubbeo, in The Women of Warner Brothers, thought Lorre's "wildly over-the top performance" had "elevated the movie from minor horror to first-rate camp.

[40] After World War II and the end of his Warner contract, Lorre's acting career in Hollywood experienced a downturn[41] He concentrated on radio and stage work.

[42] In the autumn of 1950, he traveled to West Germany to make the film noir Der Verlorene (The Lost One, 1951) which Lorre co-wrote, directed and starred in.

According to Gerd Gemünden in Continental Strangers: German Exile Cinema, 1933–1951, with the exception of Josef von Báky's Der Ruf (The Last Illusion, 1949), it is the only film by an emigrant from Germany which uses a return to the country "addressing questions of guilt and responsibility; of accountability and justice."

[43] In February 1952, Lorre returned to the United States,[43] where he resumed appearances as a character actor in television and feature films, often parodying his "creepy" image.

[47] Having quickly gained 100 lb (45 kg) and not fully recovering from his addiction to morphine, Lorre suffered personal and career disappointments in his later life.

Being Warner Bros. cartoonists' favorite characterization, Lorre was regularly caricatured in numerous Looney Tunes and Merrie Melodies animated film shorts, including Hollywood Steps Out (1941), Horton Hatches the Egg (1942), Hair-Raising Hare (1946), and many more through the 1940s and 1950s.

[54] He obtained a few small acting roles as a result, including a brief uncredited appearance as a cab driver in Alfred Hitchcock's Torn Curtain (1966) starring Paul Newman and Julie Andrews.

The World/Inferno Friendship Society's lead singer Jack Terricloth describes Lorre as "a strangely charismatic, extremely creepy person, which I think most punk rockers can identify with ...