The Other Darrin - Due to the voice actors used for Dynasty Warriors 5 and Samurai Warrior 2 being from different companies (Voice Group and Agile Sound respectively), the Samurai Warriors characters had to be recasted with Voice Group VAs.
Post Script Season: Debatable whether or not it was planned from the start, but even though 3 was touted as being the final game in the series and thus the Hydra plotline being the Grand Finale, the plot was extended by four more chapters in 3 Ultimate, introduces a new villain which takes center stage after the Good Ending, and also provides some more backstory on the Mystics.
Relationship Voice Actor - Gracia and Sima Yi can have special relationship in the third game. Both are voiced by real-life married couple, Jun Shikano and the late Tsuyoshi Takishita, respectively.
Talking to Himself: Happens constantly with some of the characters who both share the same voice actor and have a bond with one another. Exemplified in the Japanese dub by Daqiao and Xiaoqiao, Jia Xu and Motonari Mori (who got a scenario where they interact a lot), Nene and Ayane, Motochika Chosokabe and Sima Shi, Nuwa and Kaguya, etc. However, While Achilles is voiced by the same guy who voiced Cao Pi, the two characters never share a scene together.