Early work
Finding himself penniless, Brennan began taking parts as an extra in films at Universal Studios in 1925, starting at $7.50 a day, equal to $138 today. He wound up working at Universal off and on for the next ten years.
His early appearances included Webs of Steel (1925), Lorraine of the Lions (1925) and The Calgary Stampede (1925), a Hoot Gibson Western. Brennan was also in Watch Your Wife (1926), The Ice Flood (1926), Spangles (1926), The Collegians (1926, a short), Flashing Oars (1926, a short), Sensation Seekers (1927), Tearin' Into Trouble (1927), The Ridin' Rowdy (1927), Alias the Deacon (1927), Blake of Scotland Yard (1927) (a serial), Hot Heels (1927), Painting the Town (1928) and The Ballyhoo Buster (1928). The latter was directed by Richard Thorpe who would use Brennan as an extra several times on films.
Brennan had minor roles in The Racket (1928) from Howard Hughes, The Michigan Kid (1928), Silks and Saddles (1929), The Cohens and the Kellys in Atlantic City (1929) and Smilin' Guns (1929) and The Lariat Kid (1929) with Gibson. He also worked as a stand in.
Brennan was in His Lucky Day (1929), Frank Capra's Flight (1929), One Hysterical Night (1929) (a bigger role), The Last Performance (1929), The Long Long Trail (1929) with Gibson and The Shannons of Broadway (1929).
Other Brennan appearances included Dames Ahoy! (1930), Captain of the Guard (1930), King of Jazz (1930) (Brennan said he played nine parts but when he saw the film "I sneezed and I missed myself"), The Little Accident (1930), Parlez Vous (1930), (a short), See America Thirst (1930) with Harry Langdon and Slim Summerville and Ooh La-La (1930), (another short).
The following year Brennan had more small roles in Hello Russia (1931, a short with Slim Summerville), Many a Slip (1931) with Summerville, Heroes of the Flames (1931) a serial with Tim McCoy, Honeymoon Lane (1931), Dancing Dynamite (1931), Grief Street (1931) directed by Richard Thorpe and Is There Justice? (1931).
Brennan had a bigger role in Neck and Neck (1931), directed by Richard Thorpe. His parts tended to remain small, however: A House Divided (1931) for director William Wyler, Scratch-As-Catch-Can (1931, a Bobby Clark short directed by Mark Sandrich), and Texas Cyclone (1931, a Tim McCoy Western featuring a young John Wayne).
In 1932 Brennan was in Law and Order (1932) with Walter Huston, The Impatient Maiden (1932) for James Whale, The Airmail Mystery (1932, a serial) and Scandal for Sale (1932). He did another with John Wayne, Two-Fisted Law (1932) though the star was Tim McCoy.
Brennan was in Hello Trouble (1932) with Buck Jones, Speed Madness (1932), Miss Pinkerton (1932) with Joan Bennett, Cornered (1932) with McCoy, The Iceman's Ball (1932, another short for Sandrich), Fighting for Justice (1932) with McCoy, The Fourth Horseman (1932) with Tom Mix, The All American (1932), Once in a Lifetime (1932), Strange Justice (1932), Women Won't Tell (1932) for Richard Thorpe, Afraid to Talk (1932) and Manhattan Tower (1932).
Brennan was in Sensation Hunters (1933) for Charles Vidor, Man of Action (1933) with McCoy, Parachute Jumper (1933), Goldie Gets Along (1933), Girl Missing (1933), Rustlers' Roundup (1933) with Mix, The Cohens and Kellys in Trouble (1933) for director George Stevens, Lucky Dog (1933) and The Big Cage (1933). His scenes in William Wellman's Lilly Turner (1933) were deleted.
Brennan did another serial, The Phantom of the Air (1933), then Strange People (1933) for Thorpe, Meet the Champ (1933, a short), Sing Sinner Sing (1933), One Year Later (1933), Sailors Beware! (1933, a short), Golden Harvest (1933), Ladies Must Love (1933), Saturday's Millions (1933), Curtain at Eight (1933) and My Woman (1933).
James Whale gave him a bit part in The Invisible Man (1933) and he could be seen in King for a Night (1933), Fugitive Lovers (1933), Cross Country Cruise (1934), Beloved (1934), You Can't Buy Everything (1934), Paradise Valley (1934), Radio Dough (1934, a short), The Poor Rich (1934), The Crosby Murder Case (1934), George White's Scandals (1934), Good Girl (1934), Riptide (1934), Uncertain Lady (1934), I'll Tell the World (1934) and Fishing for Trouble (1934, a short).
Brennan was in the Three Stooges short Woman Haters (1934), then did Half a Sinner (1934), The Life of Vergie Winters (1934), Murder on the Runaway Train (1934), Whom the Gods Destroy (1934), Gentlemen of Polish (1934, a short), Death on the Diamond (1934), Great Expectations (1934), Luck of the Game (1934), Tailspin Tommy (1934, a serial), There's Always Tomorrow (1934) and Cheating Cheaters (1934).
Brennan was back with McCoy for The Prescott Kid (1934) and could be seen in The Painted Veil (1934), Biography of a Bachelor Girl (1935), Helldorado (1935), Brick-a-Brac (1935) an Edgar Kennedy short, Northern Frontier (1935), The Mystery of Edwin Drood (1935) and Law Beyond the Range (1935) with McCoy. He also had a brief uncredited role in Bride of Frankenstein (1935) starring Boris Karloff as Frankenstein's monster.
Around this time, Brennan received what he later described as "the luckiest break in the world." He was acting in a fight scene when an actor kicked him in the face and knocked out all of his teeth. As a result, Brennan wore false teeth. He said, "I looked all right off the set, but when necessary I could take 'em out and suddenly look about 40 years older."
Brennan appeared in another Three Stooges short, Restless Knights (1935) , and a short titled Hunger Pains (1935).
