There's another Fiddie/Gainsbourg mash up (this one), but mixing Initials BB with Many Men is better, more aggressive, ballsy. Youtube has lots and lots of great Serge-mashups by the way. Take this one. Or this one. This is one of the bestest remixes on YT. Grandmaster Pierre Elitair gave me a cd with some of his own mashups. Here's two fine ones.
Serge Gainsbourg vs 50 Cent - Initials 50 C
Roxanne Shanté vs Anna Karina vs Serge Gainsbourg - Roxanne Girl
Dr Dre vs Serge Gainsbourg - Les locataires de Dr Dre