Anschluss

референдум был, но типа крымского

A referendum on the Anschluss with Germany was held in German-occupied Austria on 10 April 1938,[1] alongside one in Germany. German troops had already occupied Austria one month earlier, on 12 March 1938. The official result was reported as 99.73% in favor, with a 99.71% turnout.

булютень:

пральный ответ в большой кружке, результаты:

Austrian Anschluss referendum
"Do you agree with the reunification of Austria with the German Reich that was enacted on 13 March 1938 and do you vote for the list of our leader Adolf Hitler?"
Location	Austria
Date	10 April 1938
Results Votes %  Yes 4,453,912 99.73%  No 11,929 0.27% Valid votes 4,465,841 99.87% Invalid or blank votes 5,777 0.13% Total votes 4,471,618 100.00% Registered voters/turnout 4,484,617 99.71%

в 1934 году был референдум в Италии, но без ввода войск, как и в СССР