One of the oddest stories of W.W.II is this captured Lockheed P-38 Lightning. It is not odd that it was captured, or that it was got airworthy again. What is unique (as far as we know) is that this Lightning was used to attack American bombers, and in once case, successfully shot down a B-17 Flying Fortress.
From a forum posting (here) by 'Misyd': "On June 12, 1943, a USAAF P-38G, while on a flight from Gibraltar to Malta, got lost and landed by mistake at Capoterra, Sardinia. The Lightning was painted in Italian markings, and transferred to the Italian Test Centre at Guidonia. On August 11, 1943, chief test pilot Colonel Angelo Tondi used the P-38 to intercept USAAF bombers on their way to attack targets in central Italy. Tondi shot down a B-17F, "Bonnie Sue", of the 419th BS, 301st BG. This was the only successful interception achieved by the P-38G, which was soon grounded due to the poor quality of Italian gasoline, which corroded the fuel tanks. I believe that this is the only documented example of a captured US fighter being used to shoot down a US aircraft during WW2."
There are many more detailed 'accounts' of this event, several based on or originating from one of Martin Cadin's (fictional) flights of fancy in 'The Fork Tailed Devil'. The reality, above, is remarkable enough.