Genius Bonus: Torquemada is played by Mel Brooks. At first, it might just seem like comedic irony to have a man who led a major persecution of the Jews to be played by a Jewish actor...unless you know that Torquemada was himself ethnically Jewish.
Hilarious in Hindsight: Inverted. The narrator contrasts 'the first homo sapien marriage' with 'the first homosexual marriage' back when the idea of same-sex marriage had barely occurred to most people.
And then there's the mention of Ratatouille during the French Revolution part.
The synchronized swimmers emerging from the water with lit sparklers on their heads was achieved by filming them going down into the water and playing it backwards. It works... until you see the smoke from the sparklers go back into them.
When the Roman soldiers lying on the ground, stone from the giant blunt that Josephus lit to slow them down, the cloud of marijuana smoke is rather obviously sped-up stock footage of clouds superimposed over them.
Invoked in the King Louis segment. The king's impersonator tries to escape down a hallway from the French commoners' revolt, only to get stuck in the narrow end of the tromphe l'oeil (forced perspective) set.