Bugs bunny as Leopold!!??

There is one episode where Bugs plays the conductor Leopold and makes that large blond guy sing so long and loud that he literally brings the house crumbling down. If you know which episode I'm referring to can anyone tell me the name of the song Bugs has him sing? It's a popular opera song and I think the famous male opera singer Pavarati ( don't know of its spelled right) has done it. It's also done in the beginning of Mrs. Doubtfire by Robin Williams. Does anyone know what I'm talking about?? Thanx for the help!!!