THE DIFFERENCE BETWEEN XXVII

What's the difference between:

1. An English bariatric surgeon and his patient?
2. The purpose of a notary and a nude notary?
3. A clear day and an overcast day?

Answers:

1. One gains pounds while the other loses weight.
2. To bear witness and a bare witness 
3. On a clear day there's not a cloud in the sky, and on an overcast day there's not a sky in the clouds.

Credits:
#2: Melanie Miller
#3: Brian G. Humphreys