The Complete Guide to Anachronisms in Samurai Champloo--
Elegy of Entrapment (verses 1 & 2)
Episodes 20/21: Elegy of Entrapment (verses 1 & 2): Only one thing that I can find:
Sara's stage lighting.
Suspiciously modern-looking, as was Xavier's. Considering all the questions we've had about lighting in the series (see especially Anachronisms Guide notes for Episode 15), I think I may just have to make a blanket assumption that gaslight (at the very least) has come to the Champloo universe a lot earlier than it arrived in Japan here (1872).