(Warning: This post deals with some very important plot points in the "Thin Man" films. If you have not seen all of the "Thin Man" movies, then, you would be advised to skip this post. Here There Be Spoilers!!!)
Of course, the most obvious connection between "The Thin Man" series and It's a Wonderful Life is not through actors but through writers. Husband and wife writing team Albert Hackett and Frances Goodrich wrote the first three "Thin Man" movies--The Thin Man, After The Thin Man, and Another Thin Man. They also wrote the screen play to It's a Wonderful Life with Frank Capra. If It's a Wonderful Life has so many great lines, then, it is because it was written by writers who had written more than their fair share of witty lines.
Beyond sharing the writing team of Hackett and Goodrich, the first movie in the series, The Thin Man, also shared an actor with It's a Wonderful Life. Charles Williams may be best known to many as Cousin Eustace from It's a Wonderful Life, George's cousin and clerk at the Bailey Building and Loan. In The Thin Man he had an uncredited role as a fighter manager.
While Charles Williams had only a bit part in The Thin Man and only a supporting role in It's a Wonderful Life, After the Thin Man would feature none other than George Bailey himself, Jimmy Stewart, in a major role that was as different from George as one could get. Jimmy Stewart plays David Graham, who has long carried a torch for Nora Charles' cousin Selma (Elissa Landi). In the end we learn David is not only some poor guy suffering from a case of unrequited love, but he is stark raving mad. Indeed, Jimmy Stewart, who played self sacrificing George Bailey, is guilty of murder in After the Thin Man! Mr. Stewart would not be the only actor from It's a Wonderful Life to appear in After the thin Man. Ward Bond, who played Bert the Cop, appeared in a very small role as a party guest!
Like After the Thin Man, Another Thin Man would also feature two actors who would go onto appear in It's a Wonderful Life. Sheldon Leonard played Nick the Bartender in It's a Wonderful Life. In Another Thin Man he plays a much more sinister character, Phil Church, who has been threatening Colonel McFay (C. Aubrey Smith). Phil Church has very little in common with Nick, as he is even more menacing than Nick was in the reality in which George Bailey was never born! In addition to Sheldon Leonard, one of the police detectives in Another Thin Man is also played by an actor with a minor role in It's a Wonderful Life. Dick Elliot played the man on the porch who urged George Bailey to kiss Mary Bailey "...instead of talking her to death" and then complains, "Youth is wasted on the wrong people!"
Like After the Thin Man, Shadow of the Thin Man featured one of the leads of It's a Wonderful Life. Donna Reed played Molly Ford, girlfriend of the murder victim, Paul Clarke (Barry Nelson). Miss Reed would be the only actor in Shadow of the Thin Man who would go onto appear in It's a Wonderful Life, but the next "Thin Man" movie would make up for this. No less than three actors who would appear in It's A Wonderful Life appeared in The Thin Man Goes Home, although none of them would be in major roles. Sara Edwards, who played Mary's mother (Mrs. Hatch) in It's a Wonderful Life, played a passenger on a train. Tom Fadden, who played the bridge caretaker in It's a Wonderful Life, played another train passenger. Charles Halton, who played Carter the Bank Examiner in It's A Wonderful Life, had a slightly larger role as R. T. Tatuam, one of the employees of banking tycoon Sam Ronson (Minor Watson).
Song of the Thin Man would be the last "Thin Man" film, but like After the Thin Man, Shadow of the Thin Man, and Another Thin Man, it would have a very strong link to It's a Wonderful Life. Gloria Grahame, Violet Bick herself, played Fran Page, a very sultry jazz singer. Al Bridge, who appeared as the sheriff in It's a Wonderful Life, appeared as Nagle the Waterfront Policeman. Charles Sullivan, who played a bartender at Nick's in the reality in which George Bailey was not born, played a police sergeant.
As can be seen, it's not a simple case of character actors appearing in minor roles in both the "Thin Man" series and It's a Wonderful Life. The two leads of It's a Wonderful Life each appeared in a "Thin Man" movie (Jimmy Stewart in After the Thin Man and Donna Reed in Shadow of the Thin Man). Two important members of It's a Wonderful Life also appeared in "Thin Man" movies--Sheldon Leonard in Another Thin Man and Gloria Grahame in Song of the Thin Man. One major member of the cast of It's a Wonderful Life appeared in a minor role in a "Thin Man" movie--Ward Bond in a bit part in After the Thin Man. And then there are the bit players who appeared in small roles in both the "Thin Man" series and It's a Wonderful Life: Dick Elliot, Sam Edwards, Charles Halton, and so on. Even discounting the fact that Hackett and Goodrich wrote the first two movies, there is never anything less than one degree of separation between any given "Thin Man" movie and It's a Wonderful Life.
Today it must seem unusual for so many actors who would go onto appear in It's a Wonderful Life to have appeared in "Thin Man" films. It would be something like several members of the cast of, say, Serendipity (2001) having appeared in "James Bond" movies (admittedly it's hard seeing John Cusack saying "I expect you to die, Mr. Bond...."). What is even more remarkable it that the "Thin Man" movies and It's a Wonderful Life were produced by two different studios--the "Thin Man" movies by MGM and It's a Wonderful Life by Capra's own Liberty Films. It becomes even more remarkable when one considers that Frank Capra had not even worked for MGM by the time It's a Wonderful Life was produced. Why then are there so many connections between the "Thin Man" films and It's a Wonderful Life?
Much of it is the fact that the "Thin Man" movies were the "James Bond" movies of their day. While most series films were cheaply produced programmers, the "Thin Man" movies were very much "A" pictures. This meant that not only were the leads played by big name stars (William Powell and Myrna Loy), but that MGM would use the best of their young talent. Jimmy Stewart, Donna Reed, and Gloria Grahame were probably all cast because they were seen as up and coming stars by the studio. Frank Capra, as a director of some importance, would naturally cast big names as his leads in It's a Wonderful Life. Indeed, he had worked with Jimmy Stewart on Mr. Smith Goes to Washington. As to character actors such as Sheldon Leonard and Dick Elliot, it should come as no surprise that they would appear in both the "Thin Man" movies and It's a Wonderful Life. First, we must consider the fact that character actors generally played a specific type. Sheldon Leonard was known for playing thugs and gangsters, so he was a natural choice for Phil Church. Now he might seem like an odd choice to play Nick the Bartender, except when one considers Nick's behaviour in the reality in which George was not born--he was not a nice guy. Second, character actors tended to work frequently and in a wide array of movies, everything from programmers to major feature films. While the leads of It's a Wonderful Life appear in two "Thin Man" movies, many of the actors who played lesser parts probably appeared in other series as well. In other words, It's a Wonderful Life probably has connections to everything from "The Falcon" series to the "Blondie" series (actually, it has at least one connection to the "Blondie" series--Penny Singleton appears in a major role in After the Thin Man).
Regardless, when one becomes aware of the connections between It's a Wonderful Life and the "Thin Man" movies it makes for some rather interesting viewing. Indeed, my favourite could well be After the Thin Man. Not only do we get to see George Bailey as a psychotic killer, but we get to see Bert The Cop as a party guest. One has to wonder what the folks in Bedford Falls would think....