The Other Darrin: Uriel Septim was played by a different, unnamed local actor in Daggerfall's opening cutscene, in Oblivion he is played by Patrick Stewartnote probably chewing up a chunk of the voice acting budget: there are many, many characters, and few voices.
Talking to Himself: An unfortunate side effect of Bethesda's decision to have the game be fully voiced, while hiring only a handful of actors to voice over 1000 characters. It's quite possible you'll be hearing two NPCs conversing to each other with the exact same voice!
One VA for all Imperial Males, one VA for all Orc and Nord females, one VA for all Orc and Nord males and so forth.
What Could Have Been: In the other direction, the initial descriptions of Cyrodiil in Redguard/Morrowind were much stranger and more fanciful than what ended up in the game, featuring river dragons, singing priests covered in robes made of moths, and living topiaries of the dead emperors that could speak and move their bodies with the help of birds. The retcon was only vaguely alluded to within the byzantine Mythic Dawn Commentaries, though it's more explicit in the more lore-savvy Skyrim, incorporating an extracanonical explanation written by the writer who had described much of the original Cyrodiil to begin with.