Just watching "A Day at the Races" here, with sixth or seventh billed Leonard Ceeley playing a crooked business adviser. (Marx Brothers, 1937) I looked him up on the IMDB.com, and the results were pretty thin.
He was born Leon Seeley out in England somewhere. Changing the spelling from the "S" to the "C" must be one for the books. He was in America by 1924, and he appeared in seven Broadway shows between then and 1934, plus an understudy turn in 1955. He was only in two other movies besides "Races," plus a TV show in 1950. He died in L.A. in 1977.
When I was a kid, I would "read" the dictionary, look up one word and find other words in the definition to look up. The internet is like that. I came across an Old School Hip-Hop jam by Leonard Seeley's Heritage, which can't be a coincidence, I mean can it? It's called "Feel It," from 1981, on Zoo York Recordz (sic), distributed by CBS.
By page seven on the Google the results were getting even thinner, but I did come across a letter written to Life Magazine in 1961 by Leonard Ceeley of Los Angeles. He comments on an interview with William Faulkner that had appeared in the magazine. He quotes Faulkner as saying things in the interview like "there ain't much to it . . ." and "like I say . . ." While allowing that Falkner might have actually said these things, he speculates that TV cigarette commercials may have "weakened the whole structure of good taste in literary expression." You figure it out.
By page ten I was finding stuff like the number of people in the UK who are named "Leonard Seely," which is three.
Leonard is pretty good in the movie. He got a lot of screen time and he had a good sense of physical comedy.