Here are some Funny add-in to Notre Dame de Paris and some Mistake. Though I’m sure there are a lot more of these incidences that occurred in all the many different casts.
During Tentative d’enlèvement Phoebus sings “Je suis le capitaine chargé de la sécurité” (“I am the captain in charge of security” ), in the last performance the word “SECURITY” was written on Patrick Fiori chain mail. source
During a performance of La volupté the bed was covered with condoms. source
During Tentative d’enlèvement in a performance, Fiori replaced Esmeralda’s knife with a comb . source
During the song Je reviens vers toi Fiori instead of singing “au fond de moi c’est toi que j’aime encore” (From the depths of me, it’s you I still love) he sang “au fond de toi c’est moi que j’aime encore” (From the depths of you it’s me I still love). source
In the London production during The Bird they put in Cages Garou instead of ” do they birds they put in cages” he accidently starts to sing “do the children they put in cages” sourceFollow thehunchblog