During and immediately after World War II, millions of ethnic Germans were forcibly expelled from the countries of eastern and central Europe. Hungary was a somewhat reluctant participant in this process, starting only at the behest of the occupying Soviet forces and continuing only under pressure by the Allied Control Council. After expelling some 180,000 ethnic Germans (mostly to West Germany) the Hungarian government halted the process in 1948. In 1950 they actually rescinded the expulsion orders, opening the door for the expellees to repatriate. 
How many expelled ethnic Germans availed themselves of the opportunity to return to Hungary? I understand that, for ideological and economic reasons, the number is not likely to be very high, but it was almost certainly non-zero. (For comparison, the CIA estimated that over 90,000 people migrated from West Germany to East Germany from 1952 to 1954.) 
 Balázs Apor. The Expulsion of the German Speaking Population from Hungary. In: S. Prauser and A. Rees (eds.), The Expulsion of the 'German' Communities from Eastern Europe at the End of the Second World War. EUI Working Paper HEC No. 2004/1, European University Institute, Florence, Department of History and Civilization, 2004.
 Central Intelligence Agency. Migration from West Germany to East Germany 1952–54. Provisional Intelligence Report CIA/RR PR-150, 1956.