"Is that you, Myrt?" is a catch phase heard weekly on the then-popular radio show, "Fibber McGee and Molly".
This short, as well as a few other Warner shorts, is in the public domain, after Associated Artists Productions (which had somehow acquired the films in question and broadcast them on television in the 1960s) neglected to renew the copyright in time.
Adolf Hitler's wide-mouth yell at the end of the cartoon is done in the style of popular movie comedian Joe E. Brown.
In the telegram that Von Vulture reads, the term "ka-rear" ("corrupted German" for the word "career") is a "position of and slang term for a certain body-part" pun on the common crudely-worded expression of a threat of imminent firing, severe discipline, etc., if any more mishaps are caused/allowed by said verbally-threatened employee: "It'll be your a** if you mess up again!"