The joke worked because like all great zingers, it was unexpected.
There was a set-up and a payoff.
And then it was left behind, again like all good zingers.
If you are an actor, you can at least appreciate the total professionalism with which it was done.
While I wouldn't label this production of Sweeney Todd as garbage (although I have friends who do), it is my least favorite production of the piece and I have seen six. It is my least favorite as it took the blood, fear and emotion out and tried to make it an intellectual piece.
Sweeney must horrify the audience and shock them. This production does not. It must also present the title role as a sympathetic (albeit insane) character and this does not.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher