Guillaume Lebon is the French voice of Shawn.
But he is also Lupin (Harry Potter), Rémi (Ratatouille) and a lot of other one.
The french voice of Dule Hill is Lucien Jean-Baptiste
He also does the voice of Will Smith and he is a famous actor, writer and director.
I just looked up Guillaume Lebon. What a fantastic (and extensive) list of roles! Quite a few of my favourites are in there, too. And I notice he did the French voice of Paul Walker in the Fast and the Furious films - that made me think of the joke in Shawn Takes a Shot in the Dark. Gives it a whole new meaning, really!