Fine, I'll do you the/a favor and agree.

[99bottles]

'Fine, I'll do you the/a favor and agree.'

I know 'do a favor' is the usual structure, but here I have a feeling 'the' is better. Is it just me?

 

[emsr2d2]

I would find only "a" natural there.

 

[teechar]

If the favour was already mentioned, you can use "the". Otherwise, use "a".

A: Will you just say yes?!
B: Fine, I'll do you a favour and agree.

------------------------

A: Will you please do me a favour and agree?
B: Fine, I'll do you the favour and agree.

-------------------------------------
Note that AmE uses "favor".

 

[Yankee]

I would find only "a" natural there.

Yes, but occasionally you would hear the expression with "the" (AmE) regardless of whether subject was mentioned previously.

 

[Tdol]

Is it just me?

I wouldn't join you in this.