Once again, HoI2 feels like throwing historical accuracy out the window in my games. In spring 1940, the Soviets randomly declare war on Hungary. This then causes a chain reaction when Hungary joins the Axis a week later, causing Barbarossa a year early. Finland, Portugal, and Yugoslavia all join the Axis, but the Yugoslavians have an event which results in a coup and withdraw from the war. By fall 1940, the Soviet-German front has little changed, with the Soviets gaining the upper hand. However, Romania has already capitulated to the Soviets, and Bulgaria should be doing so anytime now. And without a land connection, Germany will be unable to help out in Greece once Italy invades, so I expect the Greeks may overrun Albania.
EDIT - And Greece just went and decided to declare war on the Soviets...