I've often wondered if the finale for the Marx Brothers' Go West was Buster's work, or at least featured some of his gags. The train/house gags with Harpo could not be more Keatonian. We know that Buster was involved with At the Circus (though to little avail--his ideas didn't suit the Brothers and there are hardly any memorable sight gags in the film), and in an early 70s interview Groucho did say that Keaton helped out with Go West. But Groucho's memory was obviously not at its best then, and the topic is still far from settled.
Just to return to this topic, I was recently reading Irving Brecher's memoir The Wicked Wit of the West
. He has sole script credit on Go West
, and talks briefly about the film. Besides noting that the train sequence was shot by the second unit, not Edward Buzzell, he also says "The special effects stuff was reminiscent of Buster Keaton, who was actually on the set working with Harpo
. We shot in the San Fernando valley and that train...well, it took liberties." [Boldface mine]
This seems to clinch Keaton's involvement with the film. Unlike Groucho, Brecher remained mentally sharp up to the end, and his recall can be trusted. The next step would probably be to compare the shooting script to the film, but until I can locate the former, I'll maintain that many of the Keatonian gags in this Marx Brothers film were actually by Keaton.