I know that Nazi UFO bases in Antarctica are a staple conspiracy theory, but is an actual Nazi presence in Antarctica plausible? Here's my idea from another thread:
For extra fun, make Hitler form research stations in Antarctica to discover links with the Aryan Super Race, guarded by fanatical SS. When the first Aryan baby is born in Antarctica, Hitler proclaims the station Neustuttgart (capital of Neuswabenland), and sends settlers, engaging in fishing and whaling.
Knowing Neustuttgart's isolation, Hitler orders vast quantities of ammo to be sent, hoping it can resist attack until the KM defeats Britain.
When war breaks out, a small British expedition from South Georgia waltz in expecting a quick victory. They're destroyed. By now Britain is under sustained attack and a Nazi antarctic base is its least worry.
Only after the US enters the war, is Neustuttgart captured.