No GDR in East Prussia?
It would be kind of hard to make it anything but a joke, considering it is a small enclave, mostly devoid of any actualy Germans by the end of WW2. In the end, the USSR took its spoils and the rest went to People's Republic of Poland, pretty much like in OTL.
How, exactly, do you propose that the Wallies advance that far into Europe in less than a year? The Germans decide to ignore the invasions in the west to concentrate on the Soviet Union?
After revision, I do not have one exact POD. The Allies choose to be a bit more aggressive and do not stick to the "broad front" strategy following their break-out of Normandy. More attention is paid to the logistics and the seizure of several crucial ports, including Antwerpen, which are captured faster. As a result, the Germans are unable to re-establish the Western front with any strength, and their losses in the withdrawal from France are bigger.
Hitler becomes personally fixated on the alarming situation in the West, giving the German military in the East greater freedom to implement elastic defence with the forces it has available.
Stalin is spooked by the quick Western advance and believing he could be deprived of his slice of Germany, he pushes for a new offensive in Poland ahead of schedule despite his generals' strong opposition. The offensive fails miserably and costs the Soviets some of their best units; the Germans establish a strong defensive position along Vistula which blocks further Red Army advance to the west. The Soviets are, on the other hand, more successful in their southward thrust through Romania into the Balkans and Hungary; however, the Germans are able to conserve their forces by withdrawing in an orderly fashion.
WW2 ends half a year earlier than in OTL, following Hitler's assassination in Berlin, which by that time is about to be surrounded by Allied forces. The new German government surrenders to the Western Allies only and the German units hold their positions in the East to the last possible moment before Western Allied forces arrive to accept that surrender; as in OTL, the strong desire to save the Fatherland from the "bloodthirsty, vengeful Bolsheviks" keeps the soldiers from just giving up and fleeing to the West.
Stalin is of course not amused and being denied spoils in Central Europe, he overcompensates elsewhere. The Cold War erupts with full strength earlier than in OTL.