I bet I’ve listened to Cotton Fields 20 times now at least… and I still laugh every time Ben digs on Katy during her banjo break. I’m sure it’s one of those “You had to be there” moments, so let me try set the stage for the folks who weren’t there.
Ben had just gone on a funny rant about how he comes up with banjo licks and Katy steals them all… and since Katy plays constantly and Ben doesn’t, she remembers more of them than he does. Katy even mentioned that Ben will play something she doesn’t know, she’ll ask him to play it again, he starts playing and then says “Wait! NO!”
That story was told before they kicked off this song, so the entire audience was in on the joke.