Born in Larbert, Stirlingshire, Scotland to Alexander and Isabella (née Henderson) Finlayson,[3] James worked as a tinsmith before pursuing an acting career.

[6][7] In May 1912 in New York City, he played a detective disguised as a teuchter (person originating from the Scottish West Highlands or Western Isles) in the stage production The Great Game at Daly's Theatre:[8][9] A reviewer in the Daily Mirror wrote: "Finlayson had an excellent opportunity, which he did not miss, for developing two characters in his one role—the simple, naive Scotsman and the artful, determined detective.

"[10][11] Finlayson later won the role of Rab Biggar in the Broadway production of Bunty Pulls the Strings by Graham Moffat,[10] then dropped out of a national tour in 1916 to pursue a career in Hollywood.

Finlayson was hired almost immediately by Sennett's rival, Hal Roach, who gave him supporting roles in his studio's Snub Pollard and Stan Laurel comedies.

"[17] But Roach staff producer and future Academy Award director Leo McCarey recognized the great potential of a Laurel-and-Hardy pairing and began developing their characters and expanding their roles.

He appeared in dozens of Roach films with Charley Chase, Glenn Tryon, Snub Pollard and Ben Turpin, and in several Our Gang shorts, including Mush and Milk, in which he and Spanky McFarland match wits in a comically adversarial phone conversation.

During the voice recording session for a Tracey Ullman Show short, Castellaneta was required to utter what was written in the script as an "annoyed grunt".

Matt Groening felt it would better suit the timing of animation if it were spoken faster, so Castellaneta shortened it to a quickly uttered "D'oh!

[24] The plaque was initially erected in Falkirk Town Hall,[24] but was subsequently displayed in Bo'ness Library as part of the HippFest 2019 silent film festival.

[26] In 2019, James was ranked number 39 in a list of Scotland's funniest 60 people compiled by The Herald in a feature trailing the Glasgow International Comedy Festival.