The Last Mystery of the 20th Century, also known as "Osamu Tezuka's Strangest Case in the 20th Century" has an all-star cast of Tezuka's most famous characters. Osamu Tezuka is invited to a new years party at a mansion owned by Dr. Tenma, and the guests attending the party are all of Osamu Tezuka's creations, suddenly Mr. Tezuka disappears and it quickly becomes a mystery special, with all of his most famous characters trying to find him before the rest of the guests show up.