A little humor to get you going on Monday morning

Overheard the other day:

Person A: Did you fart?
Person B: No, I think that was you
A: really?
B: yep.
(pause)
A: are you sure, cause I don't think that's mine.
B:  I've never been more sure.
A: hmm. I think my farts have evolved.
B: great.