Best Dialogue Between Lead and Backup Singers

"The Morning of Our Lives" is just too good for words, perhaps partially improvised?

He seemed to be always doing stuff like that anyway, so yeah.

"If it gets really really bad... if it ever gets really really bad..."
"Let's not kid ourselves. It gets really really bad."
https://www.youtube.com/watch?v=VtA869eH21c

Oh god, yeah.

Randy Newman ftw:

(Shame, shame, shame, shame, shame)
I ain't ashamed of nothin'
(Shame, shame, shame, shame, shame)
I don't know what you're talking about
. . .
(Shame, shame, shame, shame, shame)
Could be right
I've sunk pretty low this time
(Shame, shame, shame, shame, shame)
These are truly desperate times
. . .
Do you know what it feels like
To have to beg a little bum like you for love?
Goddammit, you little bitch
I'd kill you if I didn't love you so much
(Shame, shame, shame, shame)
Shut up!
. . .
If you could find it in your heart, if you got one
To forgive me
(Shame, shame, shame)
I'd be ever so grateful...
Will you stop that, please?
(Shame, shame, shame)
Will you stop that, please? I'm trying to talk to someone
(Shame)
Thank you

Ernie K-Doe - A Certain Girl

There's a certain girl I been after a long, long time
(What's her name?
Cant tell you

https://www.youtube.com/watch?v=RBeew18OmfU

Not a "best" here, but Sam the Sham's Oh That's Good, No That's Bad

https://www.youtube.com/watch?v=uheHQ23dTw4

The “what about the voice of Geddy Lee” part of “Stereo.”

Love the dialogue between Kevin Rowland and Billy Adams on 'This Is What She's Like'.

(Kevin): The Italians, I believe the Italians have a word for it.
(Billy): What word, what is it?
(Kevin): I don't really know, a thunderbolt or something.
(Billy): What you mean the Italian word for thunderbolt?
(Kevin): Yeah, something like that. I don't speak Italian myself, you understand.
(Billy): No?
(Kevin): No, but I know a man who did.

Playing the straightman role didn't make Adams sound like the sharpest tool in the box, however. See also 'One of Those Things':

(Kevin): There was just one problem.
(Billy): What was that?
(Kevin): It all sounded the same.
(Billy): You mean it all sounded similar?
(Kevin): I mean it all sounded the same.