While the in-game dialog is dubbed in 10 different languages, grunts during combat and action sequences are not (they're taken from the original Polish language version in each localization).
At the lumberjacks' camp, you can hear two of them having a conversation about wild flowers and cross-dressing. A reference to Monty Python.
Unlike the original Polish dubbing, which was highly praised on first release, most of the foreign localizations were largely deemed substandard in terms of voice acting. At least three versions (English, German and Russian) saw CD Projekt Red have the base game's dialogue entirely re-recorded for the enhanced edition's release, the first being the only one where the entire ensemble wasn't recast.
The character of Siegfried of Denesle had its facial features modeled after those of Konrad Tomaszkiewicz, writer, director and designer for the Witcher game series.
The dentist is called Zahin Schmartz: a pun on the German word "Zahnschmerz" (toothache).