Opinion: Germany had a legitimate claim on Danzig.

[The Mikado]

The German government specifically signed away its claims on the West Prussian regions lost in the First World War, so no, they didn't unless you somehow think that the government that signed the Versailles Treaty wasn't legitimate (the SPD regime was totally legitimate by right of revolution...the overthrow of the Kaiser in the days leading up to the end of the war was an established fact).  It bears pointing out that even Ludendorff, the politician of the Old Order most associated with the cause of revision of the Treaty, didn't lay into the treaty's territorial concessions until well after the war.

EDIT: Also worth pointing out that Germany's 1919 borders were still far more generous than (West) Germany's 1948 or Germany's 1991 borders.  Sometimes the cause of revising the treaty like Hitler advanced can eventually result in a revision even more contrary to your liking...

[The Mikado]

In 1939? Germany had signed the Versailles Treaty, so no. Anyways Danzig did not cause the German attack on Poland in any way or form whatsoever - and they were governing Danzig already, and had banned all other parties except the Polish minority organization. (Poland's and the League's letting that happen were violations of the Versailles Treaty, of course.)

In 1919? Yes, I suppose so.

That hardly counts.

Well, the German people had overthrown the Kaiser and demanded an immediate end of the war, and the German military leaders signed an armistice while agreeing to follow the eventual peace treaty, and then Ebert's government signed the Versailles Treaty six months later.  I'm not sure what's so out of order about the process here.